Earlier quoted context omitted.
It is politically unviable because it would basically take away the current benefits from straight married couples to further a libertarian pipe dream. Politics is the art of the possible: extending marriage benefits to gays and lesbians is a lot easier than clawing it away from all straight couples in order to satisfy a desire for libertarian ideological BS.
I'd say that the proper libertarian solution is not to eliminate those benefits, but to detach them from marriage. Handle inheritance, hospital visitation, benefits sharing, and other such things directly, instead of linked to marriage. I think it would solve what the gay marriage proponents say they want, and probably a lot of other edge cases too. Who knows how many other people out there the current options aren't…
And stuffing a few homophobes is good. They have been persecuting LGBT people for millennia so fair turnabout.