I think the distinction is both easy to make and important.
Myths are widely held to be fundamental about a thing (but not necessarily true). Red herrings, on the other hand, are a distraction that draws your attention away from the actual matter at hand.
So that said, I think what you are trying to say is that contrary to the poster, you believe focusing on these myths is a red herring and there are other fundamental reasons that lisp popularity remains what it is. I suspect because you did not articulate the difference, your discussion got sidetracked into semantics because it sounded like you were saying they were "the same thing"
My point was that it is not just myths (or red herrings either) that are holding Lisp back. There are some issues based in reality as well.