I think one of the hardest things to accept is that fascism and fascists don't need to be smart to be successful, do huge amounts of damage to institutions, and end lives.
German intellectuals thought the Nazi party was too chaotic and stupid to ever come into and hold power.
Having seen it in action I'd argue stupidity is even more dangerous. Competent evil was like Reagan and the Bushes. Nobody would argue they literally wanted to wreck America. Trump does.
I read an essay once by a historian who wrote that by today’s standards some of the Nazi leaders prosecuted for crimes against humanity would be considered not responsible for their actions due to low intelligence or severe mental illness
Sadly, it's 100 years later and history repeats itself.
(German here. The far-right AfD party keeps getting invited to political talkshows, because intellectuals are still sure they can beat them rhetorically.)
Turns out, fascism seeming chaotic and poorly thought out are excellent cloaking devices to get past the defenses of very serious people. While nonbelievers worry about rationality and logic, fascists amass power and grow their numbers.
Fascism plays on emotional reasoning, and the past decade has been a chastening experience in seeing what some folks around the original Nazis were noting.
Fascists are stupid bullies, which means they're all cowards at heart. If you confront them directly and with force they'll crack.
Don't pre-surrender.
Apparently decent people have trouble with the idea that people who seek power may not be good or honest people.
(and the people seeking power seem to believe that everyone else is as corrupt as they are)
Another thing I think that is hard for a lot of non-fascists to accept is that plenty of people who are "smart" and/or have formal higher-ed, and/or are social and/or economic elites support fascism and other forms of authoritarianism.