But “Black = bad” is not a simple argument because you cannot make that argument without backing it with a bunch of convoluted nonsense (complexity). Likewise with illegal immigration.

Racism never was (and still isn’t) simple. There were entire scientific fields developed to justify racial hierarchy. Nazism was similar.

I think this often tends to fall along political lines.

In my experience, the left tends to like simple stories ("we are poor and the capitalists are rich, so just take their money and give it to us", "if people love each other, they should be able to marry, no matter the gender"). The right tends to like complex explanations ("taking money from the rich destroys the incentive structure required for effective resource allocation", "gay marriage makes gay people happy, but destroy the Christian values on which the western society was build, and therefore may have unpredictable consequences").

Neither approach is right or wrong. The left tends to oversimplify and prioritize surface compassion above all else (the communism case), but sometimes the simple argument really is the right argument (the gay marriage case). The right tries to show off how smart and sophisticated their arguments are, and how "it's not that simple". Sometimes they get it right (such as in the communism case), but they very often try to find a "but actually" explanation where one is not warranted (the gay marriage case).

I read that left-wing people are consistently found to be much more able to process conflicting ideas than right-wing people are.