I think there is more to this story also.I think, companies should be able to show that an employee's outside endeavors is hurting the business or reputation. I think this is more easily done with a KKK member, than with a comedian.
If anything, why wasn't the comedian given a final written warning and told to stop his comedy? Then he could decide from there what he wanted to do. Especially since, according to him, other DM's were quite aware and approving of it?
I like to think there is more to the story that isn't being told, but honestly, he does sound like an employee who went above and beyond.
He did not improve his chances on getting another position by posting this video either.