Libertarians know that gay marriage at the federal level guarantees that they will get their gay marriage at the state level in time.
We were not going have a situation where Marines and Sailors and FBI men and millions of federal employees and immigrants were going to have to deal with being “family”, or “not family” during their careers of transfers and duty stations for very long, and libertarians know that.
Like that's not happening now?
You must not have been paying attention when Prop 8 hit the USSC and they dismissed it as the people of California have no standing
despite that the State's own Supreme Court had certified their standing. So, in essence the USSC said that the people have no interest in seeing their own state's Constitution upheld and that the federal judges declaring he amendment unconstitutional was right.