I feel like the religious aspect is not really the problem here. Since as with many other topics religions can give two completely opposite answers to the same question.
I like to look at the situation from a scientific aspect.
So my opinion is simple...
What is the scientific purpose of sex? Answer... reproduction.
What is the scientific function of the penis and the vagina? Answer... to fit into one another for the purpose of sperm transfer to the egg.
So then the question is... what is the function of joining together of a man and a woman in a marital bond? Answer... for the purpose of reproduction and help in raising the offspring of that union. This happens in the natural world all the time.
So what does that make a union of the same sex? Answer... an unnatural coupling of unmatched sexual organs. In other words, homosexuality is unnatural and would obviously (and logically) mean an end to an evolutionary line. (i.e. a dead end for a species)
So why are some people attracted to the same sex? I would answer that question with other questions? Why are some adults sexually attracted to children? Why do some people feel a sexual attraction to exposing themselves publicly to others?
There are always going to be deviant behaviors when you are dealing with sexuality. Because everyone has a genetic sex drive and everyone deals with it in their own way. But there is also an evolutionary purpose behind the basic genetic drives. (survival of the species)
I know that a few years back they said that they found some evidence that homosexuality may be genetic but I believe that it was more propaganda than actual scientific evidence. So as far as the homosexual genetic argument goes...
There are many (MANY) genetic malformations that can happen in an organism and many of them would be considered a negative evolutionary step.
So far as the health and continuation of the species is concerned, homosexuality is a negative step for the human race.
It seems simple to me...
(I knew my biology degree would come in handy some day)