The "pleb" part is specifically about consuming music like one does McDonald's. And the problem isn't eating McDonald's, it's eating
only McDonald's.
I've always found strange that judging musical taste (or lack of it) is so controversial compared to other forms of art. If you say that people who only watch MCU movies or haven't read more than Harry Potter/Twilight are "plebeians" (or whatever less offensive word you want to use... philistine?), you'll get way less outrage than by stating something similar about music.
In the end, I think the disagreement may stem from two points: "plebeian" is automatically seen as an insult, not a possibly accurate (if condescending) descriptor and the usual extreme relativism that caring about music is should as universal as caring about tractors.