That doesn't make any sense. 'White genocide' is a specific term used by white supremacists to describe immigration and demographic trends. What he was saying there was that all he wanted for christmas was for those things to continue. He was mocking THEIR use of that term, not saying that he wanted an actual genocide. Since there is no equivalent 'black genocide' term you can't say the same thing.
The professor made a snarky tweet that unscrupulous people could use to their advantage. It might have been a stupid move tactically, but he should absolutely not be fired.
If it was just mocking, then why did he do a follow up tweet of...
“To clarify: when the whites were massacred during the Haitian revolution, that was a very good thing indeed.”
If he was trying to troll racists, he did so in a pretty bad way.
