I bet a total Karen came up with that.
As many in the tweet thread point out. There is also a person in the thread claiming to be the tweeter's lawyer and threatening to sue people for harassment and slurs. Amusingly, when people point out that when you can say one word (Karen) but censor the other (n-word) it tells you they are not the same, the account starts to use the term "K-word".
One could get lost in analysing the connotations of "Karen" and whether there is a sexist aspect in making a particular annoying behaviour gendered and it is the type of nitpicking I sometimes enjoy, in this context I can't help but laugh at the idiocy of comparing it to racist slurs and the amount of privilege this requires.
Edit: After posting this I started suspecting a poe. The person who originally came up with Karen being a slur is serious (and an apparent Karen), but this with one I am 50/50 about it being a poe.