The 'apology', such as it was, tells us that the rant was not intended to be comedy, and that he DID lose his cool and make a fool of himself. This is quite apart from considerations about whether, and when, to use racial terms in a routine at all!
I tend to think 'political correctness' has been WAY overdone in recent years, but maybe it's dumb mistakes like this one that have helped make this issue so delicate.
People who feel they have been offended always have one recourse....they can vote with their wallets. I remember Andrew Dice Clay and his ridiculous routines a few years ago....it's not whether they were 'over the line' or not...but *I* didn't like them, so I didn't watch them after I saw the tone.....so it made sense for those in the audience to walk out on this guy. The club may not allow him in again, and we'll have to see how his 'career' goes.