I do indeed know about McCarthyism. I believe my high school US history class covered it briefly, then my English class covered it more in depth when covering The Crucible. In the US, many of the worst excesses of the FBI can be traced to J Edgar Hoover. That includes his harassment of King and murder of Hampton, but not the murder of King. My understanding is that Hoover's reign is such a dark spot because he had dirt on a lot of Congress. Once he was gone, the FBI got reigned in a lot. We know of programs like COINTELPRO because of the US Senate's Church Committee report. I'm skeptical that a thin-skinned authoritarian regime would do that sort of investigation.

All that said, there are still way more freedoms to speak your mind. I can go protest a government decision in the streets and generally things stay pretty calm. Even protests that go sour don't usually go that sour in the modern day. And there are lots of ways to influence local decisions that the left especially underestimates.