Communism isn’t a thought crime.
Communism is the rejection of private property norms.
It’s not possible to determine that someone is a communist or that they prefer communism by their thoughts alone. After all, none of us are mind readers. In order to determine whether someone is a communist, the person in question must first demonstrate their preference for communism through purposeful action. Verbally expressing that you prefer communism does not create a victim (and as such is not a crime), but it does demonstrate both a preference for the subversion of private property norms and an intent to act on that preference in the future.
The non-aggression principle is the negative obligation to which private property norms give rise. By rejecting private property norms, communists exclude themselves from appealing to the non-aggression principle in their own defense. Because if a communist were to appeal to the non-aggression principle, they’d be embracing private property norms and excluding themselves from appealing to communism.
This isn’t what happens, though. In reality, they only pay lip service to the non-aggression principle because “making the enemy live up to his own rules” is in the book “Rules for Radicals” by Saul Alinsky, an infamous communist strategist.
When a communist appeals to the non-aggression principle, he is only trying to mitigate physical resistance to the abolition of private property.
When someone vociferously asserts that communism isn’t a thought crime as a response to anti-communist action, they are merely attempting to get you off your guard so that looting you is as easy as possible.