More importantly, these recent events are being likened to the Chinese cultural revolution _by Chinese people who lived through it._ That should give you enough of a signal to understand that this is not necessarily benign and in anybody’s best interest.
I think the reason we use master and slave is simply that the words are short, equal length in both letters and syllables, and get the message across — cf leader/follower or primary/replica. I guess the last one is ok too.
Racism and inequality should be fought where possible. Variable naming is simply not such a place. Blacks will not be less repressed, women will not be less mistreated.