It should be noted, from biographies we learn he wasn't always very nice, or kind. To his friends, to his family, to his fellow musicians. He was a hard taskmaster. People say the same thing about Monk, who was also the personification of "cool" and Mingus who was red hot, but also very cool.
Miles himself would admit to not being very nice to several people. His autobiography includes many passages where he matter-of-factly recounts being cruel to people. Often these passages are him simultaneously voicing regret for his actions, but he doesn't shy away from what he's done. He owns it.
This happens several times throughout the years as he recounts events. And while he mostly takes responsibility for his actions, it seems to have been an ongoing behavior that he found himself unable to resolve completely.
I was watching a documentary on BBC about Davis (I think it was _Miles Davis: Birth of the Cool_) and was struck by one of his wives talking about his drug habits. She said that his heroin use wasn't a problem but once he started taking cocaine he began drinking more and became increasingly violent.
