You're too kind by far. A category which is cognitively economical but classes a few non-dangerous items into a largely dangerous category, or vice versa, can still be extremely useful. So a criticism which points to such an instance (Marxism) is weak. But a criticism which invents such an instance (Nazism a la Thor) is beyond weak. Categories prove their usefulness is the real world.

The problem is - to paraphrase pragmatist's summary of the Hanson-Moldbug debate - Moldbug is thinking like a(n old-school analytic) philosopher. We need to think like social scientists on this one.