Tussling with UFC champ Conor McGregor at the MTV Video Music Awards apparently wasn't enough drama for Machine Gun Kelly . Hungry for the beef, MGK recently dissed Slipknot at Riot Fest while the two were performing simultaneously on different stages. In the middle of his set, MGK pressed pause on the hip hop to address the crowd, 'Hey, you wanna know what I'm really happy that I'm not doing? Being 50 years old wearing a f-cking weird mask on a f-cking stage talking shit.' Once a wild boy, alw…

Damn.