To all those using the "homosexuality is natural" argument, Adam Carolla talked about this on a recent podcast and had what I thought was a good point. Unlike humans, most animals that engage in same-sex behavior are not exclusive voluntary homosexuals, they are just horny, dumb, and take what they can get at the moment. If one was to use this argument, one would have to find a species where it is proven that a certain percentage of animals are actually attracted to copulating with the same sex as opposed to the opposite one. Is there any species where this is the case? I honestly have no idea.
People that identify themselves as exclusive homosexuals are actually attracted to the same sex and not attracted to the opposite sex. When a dog starts humping a pillow (or another male dog) do you really think he would be choosing that over a receptive bitch in heat if one was presenting herself in the vicinity? Probably not. Probably is the case for a lot of other homosexual behavior in the animal kingdom, where it is a matter of a largely heterosexual animal undergoing a homosexual act because is is dumb and horny and there are no receptive females around. Probably the analagous situation in human populations is in prison, where a lot of dudes that identify themselves as heterosexual engage in homosexual acts for lack of opposite gender options.