I had another comment in this thread that's related to this topic maybe other people can help me out with.
I've seen others use this same logic to say that MLs are the equivalent to even lefter groups, though. Like how Soc Dems have betrayed communists, MLS have always betrayed and backstabbed anarchists. I haven't read enough history to know if that's true so I never argue this point. I guess one of the things they may be referring to is the Bolshevik 1917 revolution, and their betrayal of the elections, squashing of other socialist factions, etc?