Any Leftist that's done any real organizing has likely worked with Anarchists. Those guys hate all states, and aren't afraid to tell your classic Marxists about how some of those very left states did them realllllly bad. I don't think any leftist whos operating in good faith has a problem with real critisizm. I think they have problems with state department propaganda lines that they have to hear and refute like every time they try to talk about any kind of Leftism.
Especially since those lines are the some of the most detracting arguements there are (probably on purpose) so most times it does nothing but obfuscate the original point and move the topic of discussion away from that point.