My guess is that if you talked to enough jazz guitarists you'd encounter the same spectrum of humanity -- from dickhead to saint -- that you see in any other group of people.
OTOH, rock guitarists -- or anyone who's subjected to any sort of continuous adulation (any famous actors, musicians, whatever) -- I'm not as sure about. I think fame would often have its effect of messing up a person, losing their sense of perspective, introducing needs to put up walls, etc. That's what makes it different, not the instrument or the musical genre.