[fennecfoxen]

"Communism" as a general philosophy may not be violent, but if you look in the Communist Manifesto, and the entity which calls itself the Communist Party, the stuff they're concerned about - advocating "armed overthrow of the US government" - was a present and real threat.

Not that I'd care to throw out a blanket justification for any and all anti-Communist measures out there, mind you. But it's possible to downplay the threat excessively too.