You can't just say "government won't be involved". It's not logical at all. The homosexual lobby is trying to change things -- and the Libertarian types who say "get government out of the marriage business" are playing right into the hands of the homosexual lobby and saying "You guys are great! Yes! Let's change things!"
Marriage as an institution isn't broke. Don't try to fix it.
A government big enough to define marriage is big enough to redefine marriage.
I am still torn between advocating for 1. federal government withdrawing from marriage, and 2. fighting to defend marriage at the federal level.