A guy who, due to ego or low intelligence, refuses to acknowledge that he didn’t get understand the joke, so instead resorts to insisting that there was never a joke in the first place. He will often criticize the intelligence of the person telling the joke on the basis that they were serious.
“Make sure not to use satire around that guy! He’s Dunning-Kruger’s Kill-Joy, he’ll trap you in an argument you never actually made!”