Master/slave indicates a relationship between two things. You can have masters and slaves in mechanics, for example. We've also had masters and slaves for decades in the tech field. Drives and floppy readers used to be configured in a master/slave setting. And of course, you have masters and slaves in programming.

None of these examples have anything to do with race or human slavery. They're just a way to describe how two things interact with each other. Human slavery is called that way because the relationship between the slaves and the masters can be described by that word, not the other way around.

It's clear that we should stop using racist words with racist intentions. No-one argues that human slavery should be allowed. However, in this case, there's no intention of racism in the words, and we shouldn't stop using words just because they can be used in a racist setting. Same thing goes with black paint. It's clear that the word black is describing a color, and it is needed to correctly describe it.