To add on, I've read a little of Trotsky's whining on it and it also adds in context that prior to the KDP parliament faction agreeing to vote in a bloc with the NSDAP parliament faction, the KDP tried to form a voting bloc to do the exact same thing with the SDP.

Now Trotsky's moaning basically boils down to "you call the succdems social fascists yet you want to cooperate with them to undermine the Weimar republic and when they say no you cooperate with the fascists to do the same thing. Why aren't you launching the revolution right now? Why aren't you copying me during my golden years of the October Revolution and the Civil War exactly to the T? What are you a bunch of wimpy pacifists that hide behind the parliamentary chair? Why aren't you burning down the reichstag?"

There's little tidbits here and there of points I agree with such the section titled " "The People’s Revolution” Instead of the Proletarian Revolution " where Trotters says "The fascist Strasser says 95 percent of the people are interested in the revolution, consequently it is not a class revolution but a people’s revolution. Thälmann sings in chorus." It and the rest of the paragraph essentially says the German communists fell into the rhetorical trap of the Right by abandoning the rhetoric of the class struggle in favor of rhetoric of popular struggle, therefore trailing the fascists in the race to win the working class instead of beating it in the race.

Whether or not that's true, I haven't read anything from the KDP of that period, but the spirit of the phrase is correct.