Okay, look. My native tongue is Russian. In Russian, "being a Russian" has two forms: "Русский" and "Российский." "Ethnic Russian" and "a Resident of Russia." When translated to English, the difference gets blended, but in Russian, it still exists. We can imagine some completely imaginary English dialects in which "Lisp" would have a different meaning, can't we? We can even add some weird rules similar to "Российский Флаг" and "Русский Флаг," which would be translated depending on the context and time differently. We would have to find ways to describe "the subtle differences of 'Lisp' in different contexts." We can pretend we're talking in different dialects where "Lisp" means different things. We can create all sorts of rules and standards. But at the end of the day, for most people, Lisp is like "porn" in the sense that "if it is, you know it." I'm in that school. Clojure is a Lisp to me. Call me a religious idiot. If people can't tell the difference between Common Lisp, Lisp, and Clojure, call them idiots. I don't know, usually when I mean to say "Common Lisp" I'd say it, or I would use "CL" and people usually know what I meant. Then I don't know what we're arguing about.
I usually don't want to call people "idiots", but I would want to prevent confusion. Even though English is a Germanic language, it's not German. It's a matter of expectation. If a book title says "Lerne Deutsch" it's not meant to mean "Learn English". Same for "Learn Lisp" and "Learn Clojure". Both books usually will be about different languages. For example there was a book "The Little Lisper", for Scheme it was renamed the "The Little Schemer". People then knew that the book is using the Scheme dialect of Lisp and not Lisp itself.
Btw., even though "lernen" and "learn" are coming from a common language background (Proto German, also called Common Germanic, no joke -> https://en.wikipedia.org/wiki/Proto-Germanic_language) and here mean the same.
There's no confusion. Anyone who wants to learn Lisp can start with Emacs Lisp, Racket, Guile, Janet, Fennel, Clojure, or Common Lisp, and soon they'd know how they differ. Telling people "Oh no, Clojure is not an actual Lisp" is disingenuous. Yes, there are certain differences, but the main ingredients are there - homoiconicity, macros, REPL-driven. Sure, in some contexts, clarification is required, and usually, it is present. I have never heard anyone say something like "I actually wanted to learn Lisp, but I ended up using Clojure and never found out what 'the real Lisp' is like." When people want to specifically talk about Common Lisp, they say that. Again, I have no idea what the fuzz is about, Clojure is a Lisp. Yes, it's not Common Lisp, it's not Emacs Lisp, we know that. Most people who know just a bit about Lisps, do know that. And yet we're arguing like someone accidentally may end up using wrong Lisp and kill thousands of polar bears or something.
