I think it's particularly vitriolic because it represents a deeper social issue, the bullying of underpaid customer service employees who lose their jobs if they defend themselves. The people who suffer most from "Karenish" behaviour can't call an entitled, bullying shitehawk what they are in person so it comes out as a meme. "Doris's" sluggish driving or "Tarquin's" excessive privately-educated mannerisms are merely annoying, while "Karen's" screaming and shouting at people who can't call them out is something worse.

I suppose that doesn't change the fact it's a bit crappy for all the perfectly decent people called Karen out there. While I think this behaviour does need a good snarl word to call it out when it happens, perhaps "Karen" isn't it and we can do better.