Marriage is either a private contract, or a religious covenant.
Either way, government has NO place defining it. At all.
So we agree that there's nothing libertarian about using government to change the definition of marriage.
Only laws that don't have massive, obvious community coherence.
Murder is an obvious one. Rape another.
Abortion isn't there yet.
Abortion was "there" for quite some time, and will likely be "there" again, once people like you are ready to see sense. Perhaps when the growth and gestation of the unborn was not so well understood, your position may have been reasonable. Not so much anymore.
I guess murder is not such an obvious wrong, seeing as how you won't condemn it across the board (as in, inside or outside of the womb). But, yeah, since abortion is the murder of a small child, no one should object to abortionists being arrested, tried and sentenced, like anyone else that murders children. And, yes, many of us are willing to pass laws against it. Murder being an obvious wrong, as you say.