My take is this:
Not sure I agree with the statement that things are rarely binary, at least in this political climate. I can say with confidence that 9 times out of 10, if you are a Trump-supporting Republican versus not being one, I will disagree with you--not on one thing--but on many or all things. This is because people's views are correlated: for a given Trump supporter, if they are pro-choice and/or rabidly anti-gun control, then with pretty high accuracy one can predict that that supporter will also sympathetic to Kavanaugh over Dr. Ford, that immigrants are a major cause of crime, that climate change is a probably not happening, that the ACA is somehow immoral, etc.
People have highly interrelated views on political issues. The oddity, not the regularity, is finding a pro-Trump supporter who is pro-choice or understands that climate change is an actual threat, not a made up one. So binary thinking is pretty accurate when making predictions and assessments about people: anti-Trumpers support issues X, Y and Z, whereas Trump-supporters support A, B, and C. To be sure, binary thinking is by no means perfect, but in the case of the current political climate, particularly with respect to Trump supporters, I think it is the rule not the exception.
With respect to other politicians and their respective supporters and/or during less volatile political climates, I think binary thinking would be more problematic because there would be more nuance, shared views, and civility among political leaders. For example, witness Reagan and Bush trying to out-compassion each other with regard to Mexican immigrants. But Trump never ran on nuance and civility. He ran on destructive, divisive, and scapegoating sound-bytes that puzzlingly struck a chord with a larger number of Americans than any political analyst could have ever predicted.
