Thoughtful piece, Chris. I do think there is something inherent in the thinking of the political left and right that does affect this, which isn't talked about much in libertarian thinking circles, and that's the culture of where these interactions happen. The right is reactionary to cultural shifts, there is a case for protecting assaults on 'Chesterton's Fence(s)' (agreed rules of behavioir) that ironically allow the left and right to air their views in a civil society.
But it's a difficult needle to thread, once power is taken by either side, abuses occur, the Patriot act for the Right as an example, and the more recent examples on the Left that you gave. The US seems to have had an excellent example so far in its First amendment, but words on a piece of paper only work if the culture agrees so and power truly respects that culture.
No answers, just musings!