Arguments against those who believe homosexuality is 'unnatural'

This appeal to nature that is often made by those opposed to homosexuality is extremely weak and simply does not stand up to scrutiny. It's logical progression is that everything that is naturally occurring is acceptable and everything that is not naturally occurring is unacceptable. If we take the example of the tom cat who often eats his young should we therefore find infanticide and cannibalism acceptable? Nakedness is also natural so should we be lobbying to outlaw clothing? Not to mention the fact that biologists have documented thousands of cases of homosexuality in the natural world among other species. So if you are going to make homophobic arguments please at least try to come up with something a little better than 'it's not natural'.