Master/slave is fine main is better in other cases (I prefer main branch as it makes more sense). I've seen some reasonable arguments here and there but I feel most of the time it's just people arguing to make them feel like they are actually doing something to fix a problem (they are not)
Because we can't have both? Changing words to be more inclusive is simple. Uprooting entrenched power systems takes a just a teensy bit more effort. Come on, you can see why your argument is spurious, right?
Police accountability is just the tip of the iceberg, though. A huge issue is the fact that a lot of minority history isn't taught properly in US schools, and important events that define race relations are completely ignored. Using the term "master" to describe Git branches, for example, is just another way of staying ignorant and insensitive to those events.
I can understand that there are some edge cases where master/slave should still be correct as it is accurate, but for every other case, it's still better to use a term that is culturally aware and technically relevant, even if it's a small difference that's part of a larger cultural shift.