He was trying to be funny/troll, the problem is that he lacks street awareness and didn't see how far left shyt was going, Joe clearly did and was trying to save Ak from getting embarrassed.
I honestly think Joe dropped the mic to take some of the heat off Ak for the following reason: they would be far quicker to steal off on Ak than Joe because they have a different level of respect for Joe than Ak. Even after Joe dropped the mic Quavo felt disrespected but still sought clarification from Joe before escalating, I believe Ak wouldn't have gotten the same courtesy.