And both are traps. Saying that "someone is offended" makes it easy to dismiss them as thin skinned and emotional. Saying that "content is offensive" sends you into a labyrinth of trying to make rules about why not all offenses are equal, or else be forced to put the inevitable complaints about openly LGBT couples featuring in a story on the same footing as sexism or ethnic stereotypes.
Making it about offense at all is a dead end. What we have to ask instead is, "Does this do harm?" As I tried to illustrate in my post, these derogatory depictions do real quantifiable harm to people. If BLM isn't your cup of tea here's another example. Doctors are less likely to take women's statements of symptoms seriously because of cultural stereotypes of women being emotional and unreliable. Studies have repeatedly shown that women have higher rates of being denied necessary care because doctors didn't think they were really that bad off. When I was young one of my parent's friends died because the hospital sent her home to "sleep it off".
The entire debate has to be shifted away from either the giving or taking of offense, otherwise all we'll get is a list of forbidden naughty words without any change in the attitudes or actions those words indicate.
I appreciate the distinction you are making, but not sure if it would really solve the problem.
One group will say, "This causes harm, so needs to be changed."
Another group will say, "But does it really cause
harm? And what changes?
"
And we just shift the same dynamic to a new word: offense to harm.
The example you gave is a clear example of harm. We can extend that to racial discrimination or issues around class in terms of medical care (that is, whether one has adequate health insurance). In such cases it is clear that harm is being done.
It is less clear about D&D ideas, especially when they range the gamut, and when you factor in history, who is using the book, and the fact that it is a fantasy game. And then, of course, what changes will really provide solutions, while not creating more problems.
In the end, WotC is the final arbiter about changes. They have to find workable answers to questions like: Does a book printed 35 years ago cause harm, especially to those who don't use it? Does a written description cause harm, when it may or may not have problematic connotations, depending upon who is reading it (and how they're reading it)? What changes can we make that will address concerns around potentially harmful material, but don't open up new problems? Etc.
In other words: Best of luck, WotC!
I don't think there are clear answers, or at least ones that will satisfy everyone. As I suggested
here, probably the best answers are found somewhere between the more moderate views, rather than running with one extreme or the other. The vast majority of D&D players just want to play the game, but are open to some changes.