[update]

I don't know about Frazier, but on Malcolm X, Ali said:

Ali: Turning my back on Malcolm was one of the mistakes that I regret most in my life. I wish I’d been able to tell Malcolm I was sorry, that he was right about so many things. But he was killed before I got the chance. He was a visionary ahead of us all.

…I might never have become a Muslim if it hadn’t been for Malcolm. If I could go back and do it over again, I would never have turned my back on him.