The fight against totalitarian communism is full of great examples of the principle that if you fight against an enemy there's a tendency to become that enemy. COINTELPRO is only one example. Another is the fact that we placed much of the US economy under at least indirect state control via the Cold War national security state in order to battle the evil of state controlled economies.

I saw the same thing after 9/11 when there seemed to be a strong push for some kind of theocracy in the USA, albeit of a far lighter variety than was found in Afghanistan, and a general revival of ultra-right reactionary ideologies that somewhat resemble those of the 9/11 hijackers. We also surrendered a great deal of freedom (especially privacy) to battle those terrorists who supposedly hate our freedom.

Edit: I can keep going... during WWII we put Japanese Americans in camps.