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.