I'll take it one step farther: I'm guessing the original etymology wasn't even master/slave but master/copy. For that matter it's not obvious to me that whilelist/blacklist was racially inspired. I assume it's more like "black mark" -> "blacklist" -> "whitelist".

But you're missing the point. You can't rationalize your way out of an emotional response. You can't talk people out of being disturbed or distracted by the terms master/slave.

Rational or not, if we know that this metaphor or phrasing makes a sizable group of people uncomfortable, why would we continue to use it in technical writing or source code? It's such a small "accommodation" to ask for.