I dont think it is necessarily about the hard conversations with others. I think it is just convenient for some people to cut the world into black and white binaries and reduce other humans to one dimension.

There is a human instinct resolve ambiguity, and barring that, heuristically paper over it.

The more emotionally engaging a topic is, the more galling the uncertainty and cognitive dissonance is. The more distressing the uncertainty, the more people want a simple solution, even if it isnt true.

I think questions like if someone can be a racist AND a good person are complex. They are uncomfortable. This makes a simple answer of "NO" all the more attractive. It makes life a lot easier than if the answer is "sometimes, but it depends on 1,000 other things".

Applying purity tests to others provides an easy way to go through life while minimizing the thought and consideration given to those people.