Conservatives sometimes ask why gay marriage has to be called “marriage” at all. Why not, for example, stick with “civil unions”–or adopt some other distinctive name?
But there already is a serviceable name distinction: civil marriage v. religious marriage.
Gays and lesbians, as taxpaying citizens, don’t regard themselves as being in an inferior position to other tax paying citizens. When they go to marry, they seek the same civil marriage certificate from the registrar/recorder as heterosexuals. They don’t want separate but equal, and so a name distinction will not do in the civil realm.
If conservatives would not conflate civil marriage with religious marriage, there would be less friction here, but it’s in the interest of conservatives to conflate them. It’s disingenuous; a way of making it seem that the definition of marriage is being “taken over” by a freakish (to them) minority.
But there has never been only one definition of marriage. Catholics, for example, don’t recognize Mormon marriages beyond the civil realm. And it is only the civil definition of marriage that is being expanded to include same sex couples. No religious definition is impacted in the least (unless the religious group wants that).
Prometheus Unbound 
Make the government issue marriage certificates according to denomination and the whole thing would slam to a halt… if you made the wedding partners pay for the paperwork. No denomination? No charge. If you want a religious certificate, that will cost you.