To my understanding, Bible says that God does not like homosexual relations. But why? Why did God punish and destroy inhabitants of Sodom and Gomorrah? They were not Jewish and were not given the laws (like Mosaic laws) to follow, were they? Why were they punished so heavily?
This is different from the previous question by Mr. Spolsky: What is the halachic source for objection to gay (civil) marriage?
Judaism believes that while the complete set of commandments was given by Moses to the Jews, there are a few universal laws expected of non-Jews too (known as the Seven Noahide commandments). Genesis Ch. 2 says "therefore a man shall abandon his parents and stick to his wife"; our oral tradition (written down in the Talmud, Sanhedrin 58a ) tells us that means that only people of opposite gender should have sexual relations.
Now the why, and how exactly that gets weighed against other things, is beyond us (see the book of Job); but you'd asked about Sodom, again, Jewish tradition says it wasn't about the sex, it was about a society that had made callousness the law, and used rape to enforce that ban.
The Talmud in Masechet Hullin on page 92a says that homosexual relations was one of thirty commandments from God to the children of Noah. I can't explain WHY he forbade it to them, but this should at least explain why they would be held accountable. The point made by several people above about the specific example of Sodom and Gomorrah stands too.
Homosexual sex is called תועבה by God. The word is generally translated as abomination. The Sage Bar Kappara offers an alternative understanding in Nedarim 51a, having rejected all of Rebbi's attempts at definition; תועה אתה בה, you stray in it. Rashi and Rabbeinu Nissim explain that you forsake heterosexuality for it.
Part of the reason has to do with the deeper essence of what happens during sex.
The male sperm is not just physical material, it carries with it part of the man's soul. If used for its proper purpose, it brings life, but if not, it brings death to the world. (see more details here)
there are many sources for this, for example the zohar says when Adam separated from his wife after the sin, he had seminal emissions which created all kinds of destructive forces.
Likewise Rashi writes in parashas Noach (Bereishis 6:13): "Every place that one finds sexual immorality androlemusia comes to the world killing both the righteous and the evil."
On a personal level, sexual immorality (such as masturbation) brings tremendous sadness and this is due to these destructive forces which attach to a person who commits these things. The more severe the immorality the more powerful the destructive force and the more sadness "sticks" to the person. This is supported by the much higher suicide rates among gays than straight men. (though one can claim this is due to other factors)
Hence, much of the reason some people don't think it's a big deal is because of ignorance as to what happens during sex.
There are also practical reasons besides this such as the general moral decadence it brings to oneself and society and therefore God calls it an abomination.
Well what would you define as a wrong form of intimacy? If we are to only to view the wrongs in sexuality in an objective view. (married woman, family member) And not with a subjective wrongdoing, then we must ask why are these objective wrongs, are in fact considered wrong by the Torah.
Rav Saadia Goan (quote in the Ibn Ezra, Exodus 20) lists levels of illicit sexual actions. Based on the length of time it is wrong. A mother or father would be the worst because there is never a moment it is permitted. The married woman, once the husband divorces or dies would be permitted. He is viewing the sins in an objective manner, the worst lacking any time of permittance like homosexuality.
The subjective view to the wrongdoing of sexual behavior is lack of proper motive. (as the Rabbinic sages dispeled Yibum because of proper motive) The family member is subjectively wrong to a person, because the motive to the act will not be pure, it will lack the sanctity of such intimacy. We see this by the severity of Niddah of which the woman cannot become pregnant, and the motive will lack the purity.
Another element is the wasting of seed. The "family member" lacks ability of having proper healthy children as we can see by mere cousins. (I remember the Ibn Ezrah stating a line "planting in your own field would damage the results".) It would be a waste to the married woman as she is already being intimate. And this explains homosexuality and beastiality as well.
If you view the sins as a subjective wrong, then the lack of purity is the reason for this sin.
