Maybe there's no platonic ideal Lisp, and that's the problem, since the thing that makes programmers feel good is some vague sense that there is such an ideal. A sort of god. ;) On the level of communication and definitions though, it seems totally reasonable to me that if your goal as a community of all sorts of versions/dialects of Lisp is to unify into one standard, then you get to call your new unification the Lisp.

I see your point about arrogance, though I think the insulting tone could be turned around easily -- you have these Lisp-like languages that don't even have Lisp in their name nor a lot of Lisp's crucial features trying to appropriate/claim an inheritance on all the hard work and glory and name recognition that went into Common Lisp and its predecessors. Let them have their name. I'm a pretty big fan of Clojure (and do like what Racket is doing when I read up about it) but imagine trying to sell Clojure to an old Lisp hand with "it's like Lisp" and watching them type (inc "a") vs (1+ "a"). https://pastebin.com/kBfNvxei vs https://pastebin.com/hPB2cy1X and there's no contest. (You might win them over with further persistence but they'll probably be wondering where all their favorite parts about Lisp are in this so-called Lisp-like.)