It's a shit argument and it's ABSOLUTELY thought policing. You can't say someone will do something until there's been something done. It's just not how things work. Yes, that includes if they strongly believe that any specific group of people should be killed, for any reason, unless they've ACTUALLY KILLED A PERSON OR MADE AN ATTEMPT. Anything short of that? That's called thought policing bud.

Unless you're not talking modern-day Nazis. If you're just talking about the WW2 Nazis that actively rounded up Jews and didn't see any problems with it, well... Yeah, we went to war over that. It was one of the few good reasons for a conflict. That's dead and done.