Princeton philosophy professor Thomas Kelly wrote a book called "Bias: A Philosophical Study" in which his central thesis is based on the principle that "bias involves a systematic departure from a norm or standard of correctness." He's not talking (specifically) about political correctness, but about any standard by which bias can be evaluated, which might be accuracy, or legal justice, or morality, etc. Anyway, it covers a lot of ground but is fairly accessible. There isn't much jargon, and he doesn't expect the reader to have familiarity with the literature.

https://global.oup.com/academic/product/bias-9780192842954

That's something I was wondering myself. I like to read philosophy, but I don't know any references that cover the subject to a satisfying degree. Even if I go to Stanford Encyclopedia of Philosophy (a good starting point for your research with lots of pointers towards other articles and books) there is an article for Implicit Bias, but there is no article for Bias itself; this concept seems to be taken for granted and as nonproblematic.

The idea of bias is quite simple in the context of instrumental rationality: you have an objective and you optimize for it. For example, you may want to determine whether something is a face or not a face. In such case face pareidolia is a manifestation of bias.

But what is bias if we don't talk about instrumental rationality and goal-oriented behavior? What is bias in terms of so-called value rationality? There is a whole bag of those weird abstract concepts that exist as a foundation for fashionable contemporary mainstream philosophy and even beyond that as the Zeitgeist of our age. But those concepts seem to often just be asserted as an obvious starting point you have to agree with before something like (quite ironically called considering the context) Critical Theory would make sense to you.