So there's this company called Beamz who have produced a DJ controller that lets you use your hand to start and stop tracks / samples.
However they've gone all out with a promotional video with the "legendary" Grandmaster Jay (Who i have never come across in my history or reading in Hip Hop.) Who does a demonstration. He literally fakes DJ-ing a recording of Jeff's routines performed live. So poorly executed in the edit that you can hear the crowd and Skillz over the top of it.
Jeff's not been happy. The DJ world has not been happy. Its snowballed into this hate campaign against the company and this character that they've invented Grandmaster Jay.