"Not allowed to discuss ideas the governments disagree with" in a myth, a fairy tale told by the kind of people who get banned from everywhere they go for "just having different opinions."

What are the opinions? What are the ideas? The US Civil War, by these terms, could be boiled down to "a clash over different ideas", it's not a useful metric. The fact is, no government on Earth is going to let you actively advocate for their violent overthrow, especially not when theyve just clawed their independence from, in many cases, centuries of colonial rule. And when you actually look into the historical events that anticommunists gesture vaguely at as examples of "communist authoritarianism", that's what it always turns out to be. The cycle goes like this:

Western capital foments fascism--> western capital arms fascists---> western capital directs fascists against socialist state, attempts to topple government for sweet natural resources-->socialist state cracks down on fascism--western capitalist press goes into overdrive about the plight of the poor fascists-->"Actually socialism is as bad as fascism, haven't you read this article in the Bezos Post?"