You can tell people who criticize the "radical left neo-marxists" know very little, seeing as they seem to think leftists can agree on anything, ever, at all.
Conversation
Radical right wingers: "Okay, we hate all these people. Let's exclude them from society. Deal."
Radical left wingers: "Yo, I really don't respect your reading choices. Let's spend the next hour dissecting your political positions and excommunicate you if we disagree at all."
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It really isn't hard to understand why there is a fascist-nationalist upsurge even though those ideologies are pretty meh.
There is no compelling alternative that doesn't immediately fracture into 5 different splinter factions of niche interests or intractably specific idealism.