Clapton's friendship with B.B. King is only a small part of his strong positive connection with the Black blues community. Clapton spent a lot of his own money hiring lawyers to sue British blues players who had not paid royalties to Black blues artists. Among his many beneficiaries was John Lee Hooker, who bought a night club with his money from the settlement.

Clapton was not only a heavy drinker during this period of his life, he was also a heroin and cocaine addict. Cocaine produces hysterical paranoid delusions and often makes people do things they would never do straight. Clapton has been off drugs for years, and is now a very different person. If a woman has sex while intoxicated, we say she did not consent to the sex, and thus is not responsible for it. Why shouldn't the same principle be applied to Clapton's intoxicated behavior?

Another important issue was that Clapton has apologized for this outburst. He said that he wasn't speaking his own mind but was attempting to do a kind of comedy routine in the style of Monty Python, by pretending to be a bigot. He was playing with a black drummer that evening and had hired many other black musicians in the past. (I don't know whether that makes it better or worse, but it's a fact.)

Comedy was a lot edgier back then. This would still have been pretty awful in 1976, because Clapton had no talent as a comedian, and even less comic talent when he was drunk. But the Monty Pythons used blackface and yellowface in many of their routines, the assumption being that in our enlightening times, this was ridiculing racism, not racism itself. This was arguably a mistake, but the question is complicated I think. I talk about this more here.

https://teedrockwell.medium.com/the-fall-and-rise-of-forbidden-language-bb0a27152b09