“The world is not divided into either/or.
It is much more complicated than to claim a person my enemy likes has to be bad.”
Bingo!
And because many people are simpletons, unable to think critically or too lazy unwilling to make the effort, they gravitate to one end of the political spectrum or the other.
Each side exists as a home for these people. For the Nazis/fascists it was the jews who were the boogeyman, the Communists, anybody with means. Today we have new boogeymans for each side
Stalin killed more Jews than Hitler over a longer period of time.