FEMA camps and the threat of tyranny
First, let me be clear: there are no secret (or not so secret) FEMA prison camps, and if there were secret prison camps, they would be operated by the military, not by FEMA. So let’s just move that conspiracy theory off to the side, because the whole “FEMA prison camp” thing is at least two different flavors of nonsense.
However, the suggestion that such a thing could never happen here ignores a very important fact: it has already happened here.
There are people alive today who remember when FDR issued an executive order to arrest and imprison tens of thousands of US citizens (and nearly as many legal immigrants) without trial or due process of any kind — and in 1944 the US Supreme Court declared this a valid exercise of Executive power under the authority granted him by the US Constitution. That didn’t happen in Stalinist Russia or Nazi Germany — that happened here (the USA).
So while stories about FEMA internment camps is a bunch of crackpot nonsense, I think it takes a special sort of hubris to think something like that could never happen here again.