It's in my nature to treat everyone as acting in good faith, by default. So when someone would cast a judgement, even a broad one about a demographic, that I couldn't clearly acquit myself of, I would internalize that judgement and direct it towards myself.

This has proven to be totally unsustainable, at least on the internet. Still, I don't think most people make bad judgements out of fundamental malice, but out of a) lack of critical thought, and b) the phenomenon described in the original post where judgement towards others becomes a defense mechanism.

So what I try to do now is neither internalize nor outright dismiss others' vitriol, but to accept that it's probably a) rooted in something real and valid, and b) unrefined by critical thinking and also warped by social pressures to a point where it can't be taken at face value.