[Zuider]

Believing NAMBLA'a propaganda is a thought crime. By contrast, actually viewing indecent images of children involves participating in a crime committed by the creator of those images. Similarly, the demented ravings of The Daily Stormer are thought crime. Racially motivated abuse and violence are actual crimes.

[bduerst]

You just reiterated my point:

Thought crimes can involve participating in, or contributing to, crimes committed by other people (as you just elaborated).

That's why as a society we ban consumption of child pornography and other types of thought crimes - because they involve harming others.