In addition to the Brownshirts murdered during the Night of the Long Knives brought up by antithesis, Communists and Socialists got to warm up the concentration camps prior to its more well known prisoners. For a shortened period, natch.
Hitler, the darling idol of the Fart Reicht, had something of a renowned disdian for "decadent" and "degenerate" arts and other cultural 'flotsam' he saw staining his adopted poor post-Great War Germany and the Weimar Republic's Socialist leanings as well as other such progressive movements in the 20th Century.
He claimed Marxism was a tool of Zionists bent on world takeover, something to be stamped out in a lil' shindig later referred to as WWII.