The saddest thing about Ali's life IMHO is that he lived in a world where the best way he could make his living was hitting and being hit by others. It is time to recognize boxing for the barbarism that it is and retire it from the repertoire of human activity along with bullfighting and bear baiting.
It's not barbarism when it's consenting adults. Bulls and bears do not consent.
Do you think this is OK?
https://en.wikipedia.org/wiki/Bumfights
The barbarism in bull fighting and bear baiting lies not in the animal's absence of consent. Animals don't consent to be eaten, but eating animals is [EDIT] not generally considered barbaric. What makes boxing and bull fighting and bear baiting barbaric is the fact that the object of the game is to inflict pain on another living being. Many other sports have pain as a consequence (football, rugby), but in boxing the goal is to inflict pain. The more pain the better. The ideal outcome is to render your opponent unconscious. That, IMHO, is barbaric.
Money and social constraints also significantly distort the matter of consent. Muhammed Ali was a black man living in an age of discrimination. His professional prospects were limited more by the color of his skin than by the content of his character. I think he was capable of a lot more than bashing people's skulls in. But because society places so much value on bashing people's skulls in, we will never know.