First, a little disclaimer. I am in fact a homosexual, and I am in fact a Muslim (a very un-orthodox Muslim, but a Muslim none the less).
There are two major arguments that have been put forth against homosexuality that not only are incredibly silly, but factually incorrect. Let's start with the first one.
1: "Homosexuality is unnatural"
If this is the case, why is it practiced not only by humans but by many other animals in the animal kingdom, most notably Zebras? Moral/Religious opponents of Homosexuality seem to have it in their heads that humans are the only species on the planet that practices it, when this is not true. So if it is not only practiced by humans but by many animals in the animal kingdom, how can you possibly make the case that Homosexuality is unnatural?
2. "No one is born a homosexual"
This is factually incorrect. I don't personally believe that science has all of the answers, but if science hasn't proven anything else, it has proven conclusively that homosexuality is the result of hormones that the mother's body pumps into the child during pregnancy. I would post the links explaining all of this, but I'm a new member and as such I'm not allowed to post links. So the entire notion of homosexuality being a personal choice has been proven to be factually incorrect.
I recommend everyone watch the documentary, "For the Bible Tells Me So." You can find it on Netflix.