Allaah Almighty says in the Qur'an:
“And (remember) Loot (Lot), when he said to his people: ‘Do you commit the worst sin such as none preceding you has committed in the ‘Aalameen (mankind and jinn)?
Verily, you practise your lusts on men instead of women. Nay, but you are a people transgressing beyond bounds (by committing great sins)’”
No-one before the people of Prophet Lut commited that act, and there were many centuries and/or milleniums before that when men and women lived and had perfectly normal relationships, yet they never commited that sin.
Anyway, this is what brother Ansar said in another thread:
Homosexuality - including both gays and lesbians - is seen as a perversion of the natural order which God has instituted for humanity. It is in conflict with the nature of humanity, as a creation that procreates. Hence, it is wrong from a natural perspective. Homosexuality entails many dangerous practices that have disastrous medical consequences. Hence, it is wrong from a medical perspective. Homosexuality negates the basic block of society, a family, thus it demolishes social order at the grass roots level, as children are no longer raised with the compassion of a mother and guardianship of a father. Homosexuals consume from society yet contribute nothing in return. Hence, it is wrong from a societal perspective.
He also said something related to this issue of genetic v environmental
Again, as I already pointed out, there is much support from the scientific community to suggest that homosexuality is caused by environmental factors, not genetic. I don't have a problem if you want to believe that its genetic, since it makes no difference to my argument, but you have to recognize that there is another scientific view on this as well. The two views:
1. genetic- people are born either homo or hetrosexual
2. environmental - homosexuality is a condition which develops in someone due to external influence
Therefore even if you linked that site using the argument that it's genetic, and even if we were to 'believe' that it is genetic, there are many other scientists who disagree and say that its purely environmental.
Now the Question might come up:
"If that's the way they were born, why did Allah make them that way?"
Okay, so let's suppose that view 1 (genetic) is the correct view. So why did Allah swt create them with homosexual tendencies? The answer is simple - it is a test for them. They must not act on these desires but must bear patiently and restrain themselves. Just as people born with the desire to commit fornication and must restrain their desires. Disabled people may have to restrain their desires for their whole lives and bear their condition patiently.
And Allaah Almighty knows best.