First off, on the religion thing: Don't make laws that force people to live according to your religion. Religion is a choice. If people choose not to make that choice, that is their right. It means nothing to God if they're being forced to live that way anyway.
Second, on anatomy being made "solely for reproduction purposes."... why is it so damn pleasurable? Heck, sex can be a whole lot of fun. It's also great excercise, and it relieves stress. It also is a great way to bring a couple together in a deeper way. Reproduction is the end result, yes. But why throw away all those other great benefits just because you don't want the end result.
Third: What's the big deal? What's it to you if two gay guys wanna get hitched? Are you somehow being hurt by it? Does it cheapen your marriage or the marriages of any other straight people? Do you think that suddenly your son is going to want to be gay and homosexuality is going to become the "in" thing, like bell bottoms and Britney Speares?
Hardly. It's pretty clear at this point, despite what the conservative right and religious elite would have you believe, that homosexuality is not a lifestyle choice, but rather biological. You can't help who you are, so why should you be given the shaft by society for it? Like Skinwalker said, it's the same as racism.
Feet were made specifically for walking/running/standing. Therefore, using them to drive cars is wrong.
Ears were made for hearing. Therefore, piercing them is wrong.
Tongues were made for tasting. Therefore, french kissing someone is wrong.
See? None of those make sense, do they?
Face it. This all comes down to religion. People dislike homosexuality on the basis of religion, and then try to come up with reasons beyond the Bible to justify it to non-religious people.
"Not all one pleads can be granted. But a good hearing soothes the heart." -The Instruction of Ptah-hotep.
"So here I go, it's my shot. Feet fail me not. This may be the only opportunity that I got..." -Eminem