Personally I view both as two sides of the same coin. Both the alt-right and the social justice left are totalitarian, intolerant, and intellectually shallow. I find their argumentative styles, emotional reactivity, and style of engagement with the larger culture to be strikingly similar to the point that I see them as different manifestations of some underlying social or psychological disorder.
I actually used "vouch" on this one, which I rarely do, because it's interesting and a bit more substantial than the usual fare.