The law is the law. Just because what your religion may tell you, the law is the law. And if you're paid to uphold it, do your damn job or quit.
If you don't approve of gay marriage, don't fucking have one.
If you don't approve of abortion, don't fucking have one.
Not so long ago, we'd have been having this discussion because some redneck asshole refused to issue a marriage licence for a mixed race couple. In twenty years, the only people still bothered by this will be the same ignorant bigoted fuckwits who still think "mixed marriages" are a problem.
Go thump your books and get the hell out of other people's lives.