Guys have been called “dick” forever now. Words like “Karen” provide a very clear mental image of a specific type of “asshole.”
I do feel like we shouldn't attach that to a real name that real people have, but instead use actual words like "entitled asshole" that convey the same meaning without lumping in unrelated people who so happen to share the name who have done nothing bad to anyone.
I always think "douchebag" is quite good for this. You can really pile quite a lot of emphasis onto that first syllable for maximal invective effect.
The origin of "dick" is, nevertheless, the name "Dick". Would you be satisfied if we went from "Karen" to "karen"?