I agree-- in part --management is free to make lousy decisions, to reward mediocracy, and to cut costs in nonproductive ways and for that matter to assign folks who work harder than the norm to menial tasks and other foolish things--nothing illegal about poor management. Nothing improper about seeking cheaper labor
I don't see ethnicity as being his basis for poor treatment --its not uncommon that harder workers or producers get sabotaged ---However I have seen were a handful of ethnic comments from a manager have killed the management side IF discrimination case arises ---big time. Example : Black female boss made several comments about too many white guys around here --management paid big time for that. Example White male boss made several comments about no Black would get ahead of his level while he had anything to say --management paid big time for those loose lips.
Me, I'd keep careful written records someplace safe off site of each such name slur by a boss and each meeting I was excluded from. May or may not be useful downstream.
Time to seek better options elsewhere? Vote with his feet when he gets better slot lined up elsewhere.
Do not get huffy and 'quit"--that's fatal to UC issues.