Except that’s not what legalizing gay marriage does. You can’t force a church to marry anyone. There’s a reason why I, as a Jew, would be turned away at a church if I tried to marry my (baptized but nonreligious) SO there- it’s the parish’s decision on whom they marry in a church, and they wouldn’t marry us- we know, we checked for shits and giggles, and they don’t perform unions of Christians and non-Christians.
Just like how atheists get married even though- shocker!- they aren’t religious.
Think of it as two separate entities- religious marriage and civil marriage. Religious marriage is whatever the hell your church, temple, G-d or gods want to call it. That has nothing to do with the government, and the government can’t legislate on it.
Civil marriage, on the other hand, deals with things like spousal pension benefits, tax breaks, custody agreements, adoption rights, hospital visitation rights, power of attorney, military benefits, insurance benefits, etc.
No one is going to make a church perform a marriage they don’t agree with- even if it is just that particular priest or pastor. And you know what? We don’t give a shit if the church recognizes them as married or not- interestingly enough, the church or churches are not the center of everyone’s world. The legal benefits of marriage are what is important, as well as the legal legitimization of the union.
Rebloggable by request (my imgur screencap is not big enough to copy my whole answer because I’m super wordy and stuff, so you all get a copy-paste! Original post here)