Sexuality is natural yes. That is pretty much a tautology. But who says sexual orientation is not a meme? A powerful and primitive one yes, but a meme still? It surely makes more sense to me than to think it's some sort of genetic feature, in which case homosexuality would be a defect that managed to elude hundreds of thousands of years of natural selection, or that is so common a mutation as to suddenly re-appear with so much frequency (if this is the case, then it should be quite easy to pinpoint genetically).
The fact that religion (or some sort of mystical worldview) has sprouted pretty much in every human culture independently suggests that there probably is some natural propensity to be religious. In fact, it takes education and training in critical thinking to effectively shut down the religious meme.
So, you could reasonably argue that both phenomena are not that different. That both are memes. And both have, like it or not, an influence and power that can profoundly affect the basic core of human society. And if sexual orientation is not a choice, the fact that a supernatural worldview might creep in your head might not be a choice either. So maybe you should be more careful with the vitriolic attacks on religion, as you might be discriminating people for something that they can't control (without some help at least).
But hey, I know these days it's so PC to defend the right to sexual orientation and it's so fashionable to attack religion... Not that I'm claiming you do it for these reasons. But I find it curious how we so suddenly jumped from homosexuality being a taboo sickness to being an unattackable right (while at the same time not being a choice). It seems to me no one is trying to understand it anymore, which, in turn, means it can suddenly become a taboo disease again, should the winds change direction again. But oh well, this is just me ranting...
My point is, we actually don't know where sexual orientation comes from (and apparently no one cares) and we also don't know where religion comes from (or why it's so hard to make it go away), therefore, viciously attacking one while piously defending the other (seems to me it) is probably a bad idea.