Well, humming most of the time, suggests a musical personality
concerned more about calling attention to himself than to the music. His
disinclination to perform all but "heavy" works. His contempt for public
performance. His holier than thou pronouncements about the immorality of
"ordinary" human beings. His cold-blooded, unapologetic and flippantly
annotated mutilation of his recording of the Beethoven Appassionata sonata.
Additionally, I make that assessment about him based on a general
impression of the man derived from all the factors mentioned above as well
as less easily quantifiable observations I've gained from his writings,
photos, musical style, etc. I simply felt the man to exude an immodesty
and preciosity about himself that annoys me.
Your remark that I would have to know him personally in order to lend
credibility to my view of the man is a dubious suggestion. It means that
we can say nothing about anyone not in our immediate family or in our most
intimate circle of friends. And even then, can't we can question the
validity of observations made about people we know intimately on the
grounds that we're "too close" to them to know them impartially and in
a balanced manner?