Not to mention, not all religions are opposed to same-sex marriage - the UK Quakers have been agreed for several years now that they want to be able to marry same-sex couples.
And there are no real reasons against it that don't boil down to "I don't like queer people and don't think they should get the same rights as me". I also put quite a lot of strident comments into the form!
/has a lot of ~feelings on this