I don't think it's because people are offended at the use of the word master, in this case. I think, that it's symbolic. By making a point of getting rid of the word master, you're showing that black lives matter.
Are we going to get rid of every word that a plantation owner ever used to insult the slaves? For words that specifically have no purpose other than conveying hate, I can understand stamping them out. But master has quite a few other meanings, most of which I would think existed before institutionalized slavery of black people existed. Seems a bit unproductive to target it. They had supervisors - should we stop using the word supervisor? What about boss? Or plantation? Could not the entire BDSM culture be considered in the same way, with its themes of bondage and servitude? Somehow I doubt that every time a sub asks a dom to crack a whip over their head they are celebrating slavery. How close does a word have to be to an issue relative to its other usages in order to be considered a symbol of that issue above all else?
It wasn't intended to be. It's an actual question - where does the cutoff point lie for something standing on its own vs it being considered a problematic and irredeemable symbol of an atrocity and how do we define it? How do we differentiate between when someone is an asshole or not?
I came across an example of this the other day after seeing the word used in a historical text for a class [0,1]. I was fairly certain it did not mean what it sounded like it meant so I looked into it. While the word does not have a definition associated with slavery (that I know of) and is thus arguably further away from the issue than the word master, its phonetics are enough for its usage to result in condemnation.
Lives can be ruined, either from an accusation over a misunderstanding or a failure to recognize actual harmful intent. Vagueness creates friction. To solve a problem there needs be a thorough and precise understanding, and when it involves multiple people there also needs to be a sufficiently common definition.
Please don't bring up tired tropes like that one here. It's never going to change, so we're only going to get a tedious flamewar out of it, which indeed you've been perpetuating downthread—which, please don't.
It's not as if we lack for new things to discuss and argue about.