It can go both ways. Bad actors can simplify because it leads to indifference, by way of generalizations. "black" = "bad", "illegal immigrant" = "gang member". It's how racism works.
> The “good” side therefore needs to fight that complexity with simplicity and empathy.
Empathy, yes. Simplicity doesn't normally lead to empathy; complexity does.
I read that left-wing people are consistently found to be much more able to process conflicting ideas than right-wing people are.
40 years of experience has taught me that absolutely no one is less able to process conflicting ideas than left wing people are, and it's not close.
Political extremes will be extreme. Centrists can hold both.
AFAIK this generally isn't true. About the centrists, I mean. Most self-identified centrists are just moderate right-wingers.