This is one of the things where the nature of the modern United States makes it hard. I routinely go around telling people that the current regime in Washington is illegitimate, nobody should obey them or listen to their lies, and that I look forward to the day they're ripped from their thrones and tossed in prison. In most places and times saying that would make me a revolutionary, but in the US it's not even arguably a crime.
Usually, it's a crime when people do stuff. Complaining that the government is bad is free in almost all democracies.