Alright, I'll bite.
Homosexuality is contradictory to the evolutionary process of a sexual species like Homo Sapiens. Scientifically, homosexuality is a epigenetic aberration brought on by a rare set of factors coming together in the womb during development. Take a look at research by a group called NimBIOS.
I believe homosexuality is no more than a choice.
Do you "believe" in eye witness accounts? First hand experiences? Because I can assure you, there was no choice in who I was attracted to.
Same sex behaviors and even life-long same sex pairings have been observed in hundreds of animal species, humans chief among them. (And in humans, since the beginning of recorded history.
Animal species have been observed changing their gender to adapt to changes in their Eco-systems. It is not a stretch, by any means, to see the necessary evolutionary role of a percentage of a population not meant to procreate.
There is also the possibility that human sexuality is considerably more fluid than our Puritanical roots allow it to be.
Not that any of this is relevant since legal, adult personal choices should have no bearing on whether you get access to equal rights.