I’m not sure pandering to their comfort is the right thing to do here.
Why are they associating “master branch” with slavery in the first place?
I’ve spoken to multiple black Americans internally about this and they strongly associate “master” with slavery since members of their families where literally owned by people and had to call those people “master”.
Maybe it would matter to them less if the US had abolished slavery and made people of all color equal, but since we instead created racist policies that historically put non-whites at a disadvantage, I can see how they have a strong dislike for that word.