With his "Dance for me, boy" comment, I'd cut him some slack. I've always thought the use of the word "boy" is prone to hypersensitive reactions from blacks. "Boy" can be used as opposed to "man", where you're trying to demean you're opponent. Have the recipient be white, and it'd be no issue at all. That's a tough one to call.

But when given the opportunity to clear the air, McGregor goes a bit further and calls himself black from the waist down. That was a bit more unfortunate, and probably lends more credence to the "racist" accusations.