Sly’s brain was lost a long time ago.
In that clip Cassius Clay is spouting black separatist crap that Martin Luther King denounced. MLK said they (groups like the Nation of Islam) were every bit as wrong as the KKK.
And Clay’s parents did not support his beliefs.
Not every black citizen was on board with the rhetoric that CC was shouting but today more are. And it is because the Nation of Islam was mainstreamed in society (the MMM march in DC was CELEBRATED by the media in the 1990s with little direct challenge to the hate speech and antisemitism from Louis Farakhan and others at that event). Hippity Hoppers and athletes regularly name-check the NOI for street cred. Prisons are used as recruiting centers for black muslims.