I've been wrestling all night with the conservative claim that it's not homosexuality that they object to per se, but rather "homosexual practices."
It's pretty hard to nail them down and get them to specify exactly what "homosexual practices" are problematic, but I think it's safe to assume that it's specific sexual acts that they are talking about.
The thing is, there's nothing that homosexuals do that at least some heterosexuals don't also do, and to the best of my knowledge no married candidate for ministry has ever been asked if he or she participates in oral or anal sex with his or her spouse.
To my ears, then, the argument sounds something like this: "God hates oral and anal sex, they're abominations, unless you go to a church and hire a minister to say some magic words and fill out a form, then they're pretty much ok."
Now I know that there is more to marriage than magic words and a form, but those are the only parts of marriage that homosexuals can't participate in, so they must be the mechanisms through which sinful things become not sinful.
They never told me in seminary that ministers have the power to makes sins not be sins, but I do remember reading about indulgences, and I got the impression that we were supposed to be against them.