If I had to guess, I'd say that a lot of April Fool 'jokes' involve winding people up by leading them to believe that somethng bad has happened or is about to happen. For the White person in their cosy cocoon of privilege, such things are never really a threat, even if they do happen, there is always a way out or a way back. A Black person, however, lives under Damocles' sword, all day, every day. The threat is always real, and dressing it up as a joke once a year just rubs the reality in that little bit harder!