As these texts are translated by the King James Version, and in several other translations, you do find the same word (“abomination”) is used, but in the Hebrew text you find two different words:
Leviticus 18:22 reads:
“Thou shalt not lie with a man, as with a woman: it is abomination [tô‛êbah].”
Leviticus 11:9-12 reads:
“These shall ye eat of all that are in the waters: whatsoever hath fins and scales in the waters, in the seas, and in the rivers, them shall ye eat. And all that have not fins and scales in the seas, and in the rivers, of all that move in the waters, and of any living thing which is in the waters, they shall be an abomination [sheqets] unto you: they shall be even an abomination [sheqets] unto you; ye shall not eat of their flesh, but ye shall have their carcasses in abomination [shâqats (verbal form of sheqets)]. Whatsoever hath no fins nor scales in the waters, that shall be an abomination [sheqets] unto you.”
These two words, while they have some overlap in terms of their range of meaning, do not have the same range of meaning. The NRSV translates “sheqets” as “detestable,” which at least alerts the reader to the fact that the words are not identical. According to the Theological Wordbook of the Old Testament, the word “sheqets” is used “mostly in reference to unclean and forbidden foods… Relegating certain animals to the category of “unclean” and “abominable” may in a number of instances involve considerations of health. Yet the main consideration here must be that, whatever the reason, or however much or little it was understandable to the Israelites, certain foods were forbidden and regarded as detested. This was to be accepted on the simple basis of trust in, and obedience to God” (Vol. II, ed. R. Laird Harris, et al. (Chicago: Moody Press, 1980), p. 955).
While “tô‛êbah” can refer to that which is ritually offensive, it also includes matters that are morally repugnant, such as homosexuality (Leviticus 18:22), human sacrifice (Deuteronomy 12:31), ritual prostitution (1 Kings 14:23f), etc.
“Whereas tô‛êbah includes that which is aesthetically and morally repulsive, its synonym sheqets denotes that which is cultically [i,e, ritually] unclean…” (Ibid., p. 977).
Even when one uses the very same word, this does not necessarily mean that they carry the same weight. I can say that I love Blue Bell Ice Cream, and I can say that I love my wife, but while I would die for my wife, I will generally only buy Blue Bell when it is on sale. Though the same word is used, it is used in two very different senses.
In the case of eating shrimp vs. homosexual sex, you can tell a lot about the degree to which these things were regarded as sinful by the punishments meted out to those who violated them. In the case of eating shrimp, there was no specified punishment at all. The person who ate shrimp would have certainly been considered unclean for some period of time, pending ritual purification. According to Jewish tradition, they might also have been subject to corporal punishment. The punishment for engaging in homosexual sex was death (Leviticus 20:13).
We can also tell that these things are viewed very differently by the fact that only Israelites were expected to abstain from non-kosher food. On the other hand, the passage that the ban against homosexual sex is listed (in Leviticus 18) is in the context of a list of sexual sins for which God judges even the gentiles. This is stated before this list, and repeated again at the end of it:
“And the Lord spake unto Moses, saying: Speak unto the children of Israel, and say unto them, I am the Lord your God. After the doings of the land of Egypt, wherein ye dwelt, shall ye not do: and after the doings of the land of Canaan, whither I bring you, shall ye not do: neither shall ye walk in their ordinances. Ye shall do my judgments, and keep mine ordinances, to walk therein: I am the Lord your God. Ye shall therefore keep my statutes, and my judgments: which if a man do, he shall live in them: I am the Lord” (Leviticus 18:1-5).
“Defile not ye yourselves in any of these things: for in all these the nations are defiled which I cast out before you: and the land is defiled: therefore I do visit the iniquity thereof upon it, and the land itself vomiteth out her inhabitants. Ye shall therefore keep my statutes and my judgments, and shall not commit any of these abominations [tô‛êbah]; neither any of your own nation, nor any stranger that sojourneth among you: (For all these abominations [tô‛êbah] have the men of the land done, which were before you, and the land is defiled;) That the land spew not you out also, when ye defile it, as it spewed out the nations that were before you. For whosoever shall commit any of these abominations [tô‛êbah], even the souls that commit them shall be cut off from among their people. Therefore shall ye keep mine ordinance, that ye commit not any one of these abominable [tô‛êbah] customs, which were committed before you, and that ye defile not yourselves therein: I am the Lord your God” (Leviticus 18:24-30).
There was no mention that non-kosher foods were forbidden before the Law of Moses. For example, God said to Noah: “Every moving thing that liveth shall be meat for you; even as the green herb have I given you all things” (Genesis 9:3). And when Gentiles began entering the Church, the Apostles declared that the Gentiles were not bound by the kosher laws of the Mosaic Law:
“For it seemed good to the Holy Ghost, and to us, to lay upon you no greater burden than these necessary things; that ye abstain from meats offered to idols, and from blood, and from things strangled, and from fornication: from which if ye keep yourselves, ye shall do well. Fare ye well” (Acts 15:28-29).
And it should be noted that the word translated as “fornication” is the Greek word “porneia,” which includes any kind of sexual immorality, including those listed in Leviticus 18.
The pro-homosexual argument regarding these passages also completely ignores the vision given to St. Peter which specifically ended the requirement for Christians to abstain from non-kosher food (Acts 10:9-16), and that there are several other New Testament passages that condemn homosexuality. So the argument that Christians are hypocritical in their appeal to the ban on homosexual sex in in Leviticus 18:22, which still eat shrimp, lobster, clams, and crawfish is completely consistent with testimony of Scripture.
Somethings are inherently sinful, and somethings are sinful in specific contexts. For example, it is sinful for an Orthodox Christian to disregard the fasts for no compelling reason, and to eat a hamburger on a fast day, but there is nothing inherently sinful about hamburgers. Likewise, for Israelites, not eating certain kinds of foods had a symbolic meaning, and was a matter of obedience, but there was nothing inherently sinful about eating shrimp. However, it is inherently sinful for a man to have sex with another man, and the Bible is completely unambiguous about this.
A Recent Example:
A recent example of pro-homosexuals trying to argue against taking seriously Leviticus 18:22 by appealing to the biblical illiteracy of the average American is the following clip from the TV show “West Wing”, which “Occupy Democrats” have been circulating via social media recently, which even resulted in CNN’s Don Lemon playing portions of it:
This line of argument is really not just against the Church’s position on homosexuality. It is also an argument against taking the Bible seriously at all. No one who considers himself a Christian should have any sympathy for such arguments. But we should know how to respond to them, and so let’s look at the passages referenced in this video:
Exodus 21:7-11: This passage provides some special protections for female slaves, because they obviously were in a more vulnerable position. For more on this question, see “Stump the Priest: What about Slavery in the Bible?“, but suffice it to say here that this passage does not command that anyone own slaves, nor that anyone sell their children into slavery — it puts limits on how slaves could be treated. This was quite in contrast with Roman law, for example, in which a master could do whatever he wished to a slave, up to and including killing them, for any reason.
Slavery is no where in the Bible presented as a good thing. A Christian can certainly not own slaves and oppose most forms of slavery without violating any tenet of Scripture or Church Tradition (we still allow for involuntary servitude as a punishment for a crime, and in the form of the military draft). And so the comparison of this issue to the question of whether or not homosexual sex is a sin is a red herring.
Exodus 35:2: This passage calls for the death penalty for those who break the Sabbath. The Church still believes that the Ten Commandments, including the commandment to remember the Sabbath day, apply to Christians, but we consider the Lord’s day (Sunday) to have taken the place of the old Sabbath as the primary day of Christian rest and worship, though we also continue to observe Saturday the day of creation. The Church does not call for the death penalty for violating this, nor does it call for it in the case of homosexuality. For more on this, you can listen to the sermon:
The Old Covenant was given to people who were at a very low level of spiritual understanding. The harsh penalties that are often found in the Old Testament law were due to this. St. John Chrysostom, commenting on the law which condemned Sabbath breakers to death, said that it was “Because if the laws were to be despised even at the beginning, of course they would scarcely be observed afterwards” (Homilies on the Gospel of Matthew 39:3). But while the harsh and immediate penalties for the violation of the law are relaxed in the New Testament, the strictness of the laws themselves are not only not relaxed, but are rather enhanced. Just as you spank younger children, but expect less of them, and expect more of older children, without spanking them, the Old Testament dealt with the Israelites where they were, but brought them gradually to a higher level of spiritual understanding.
Then Martin Sheen‘s character simply begins to make stuff up. He speaks of the Bible calling for stoning someone who plants different seeds together, and burning to death someone who mixes different kinds of fabrics. While Leviticus 19:19 does say: “Ye shall keep my statutes. Thou shalt not let thy cattle breed with a diverse kind: thou shalt not sow thy field with mingled seed: neither shall a garment mingled of linen and woollen come upon thee”, you will note that it says nothing about anyone being stoned or burned alive for failure to observe these customs. This shows the complete dishonesty of those who make such arguments. These customs were part of the ceremonial law of Moses (which still has symbolic value, but which no longer directly applies in the New Testament), not the moral law of God — which was in effect before the law of Moses, and remains in full force and effect today. See: The Continuing Validity of the Moral Law of the Old Testament.