1. We make judgements on “group membership” all the time, and to the extent they’re correlated to the outcome (i.e. true) that’s not wrong or -ist. Example would be, do you avoid stepping in front of a car because you infer that the car might run you over, or do you just take your chances and hope that this individual car will stop. Ok, contrived example. How about this: people generally accept that men are more dangerous than women (e.g. when it comes to rape, stranger danger, domestic violence, courts, jails, ...) even though the vast majority of men aren’t violent at all! Is this sexist? Yes, to some extent, in particular when the state does that (e.g. always arresting men in case of domestic violence call). But at the same time, that kind of “prejudice” might just save your life; how wrong can that be?
2. Even if there’s no correlation to the outcome, not every inference is -ist. Example I mentioned downthread is, assuming that “Alex” is a man. Is that really wrong?
3. Which brings me to, you write that “treating people distinctly” is -ist. But what is treating? Again, people make inferences (that’s literally what intelligence is, short-term prediction engine). Sometimes that’s even embedded in the language (e.g. in Slovenian, you have to assume gender, unlike in English). But as long as we remain open to change, that’s fine! If the woman tells me that actually she’s “Alex”, the only actually sexists way would be if I refused to call her by her (masculine-ish) name.
TL;DR: if everything is racist, then racism cannot be immoral.
If it is based on ones favorite sports team, it is just stupid.