As acolytes of Saul Alinsky who preached the politics of personal destruction, liberals consistently demonize their opponents as either stupid or evil. Since nobody can honestly oppose their worldview, those are the only two alternatives. It's one or the other, sometimes both, but never neither.
The libs couldn't claim Nixon was stupid, so he had to be evil. They couldn't make the sale that Reagan was evil, so he had to be stupid. Infected with BDS, they raged at Bush 42 for being both.