This is a very daft argument not to say very naive.... the fact that the Nazis rose to power in Germany, one of Europe's most civilized and educated society at the time, and had support from the elite and the academics, proves that even intelligent people, if they are fed with propaganda long enough, will support extremist.
This is also the cruelty of all those regimes - scientists, doctors, lawyers etc. supported them.
I used to think like you - that extremism is only possible among ignorant people. But that couldn't be further from the truth.