I'm going to try...but I'm no lawyer.
Isn't there a law against sodomy?
For example this guy got arrested in his own home...
http://www.cnn.com/US/9811/20/texas.sodomy/
I guess it's assumed that when gay men marry the act of sodomy is destined to occur.
I suppose they ban lesbian marriages because it would upset the gay men? I dunno...this is the best I can come up with. (Am I right or...no?)
Oh wait, I keep forgetting, most of America is still Christian and that makes it a 'sin'.
How about medical aspects? There are many...sphincter problems...infections...and more (I copied the link below)
Ok good luck with it!
Ok in response to your question above. You wanted an answer, I'm doing my best...even if it's grasping at straws...I'm trying to come up with an explaination because I don't care about the law one way or the other to be honest.
My reason for sodomy being illegal could only be that it really does cause severe physical damage (not to mention spreading bacteria). Like the guy below said...insurance claims and all that jazz. It's not a good reason but it's a reason none the less.
You have to realize that a lot of people are still against gays...It's really sad tbh. Not sure what to tell you.
Ok here you go;
http://www.familyresearchinst.org/Default.aspx?tabid=102
So I was wrong. It says...
"Absent any concrete, scientific or medical reason for banning sodomy, it all became a matter of individual taste or preference. This is why the Court could say “There has been no showing that in this country the governmental interest in circumscribing personal choice is somehow more legitimate or urgent.”
You could join some sort of group to change things...