C'mon...SOME people on the left.  Or maybe us old school lefties are more reasonable than young hotheads.  But it is true that the "alt right" are certainly just as loaded up with venom now, and they've been around longer than the term...Ann Coulter, Ezra Levant, Rush Limbaugh...insulting people, shutting them down, labeling people (how the American ones especially love to call people "commies"!) 
I think the problem is less about politics and more about a general loss of civility, gullibility (on both sides) and a lack of empathy for why others think as they do.  My late father in law was exactly the sort who's get bashed by the "Marxist" left -- white, Christian, "homophobic", "misogynistic", conservative, and really, he was all those things -- but he had a heart of gold.  (Mind you, he had no patience with Ann Coulter when he saw her on TV one night...turned to me and said, "That woman's NOT a conservative...that woman's just a fool!"