Personality disorders are not stereotypes. Symptoms are not blamed on the disease; they reveal it. Would you also say, "let's not stereotype someone as disabled by speculating on whether their leg is broken just because we can see them limping and their bone sticking out?" If the symptoms are visible, by all means, let's help the mentally ill by being honest.

"Jackass" is slang for a foolish or stupid person, and as Musk has degrees in Physics and Economics from Penn, I don't think that remotely fits, unless GP was being kind. "Jackass" is also a synonym for "asshole," which is a colloquial term for narcissist.