Jack Black is trying to use his massive A-list star power to get Biden elected, something that will actually help people. Kyle Gass made an offhanded joke that could jeopardize that. So Jack Black needs to distance himself, and I'll bet you money Kyle Gass agrees with him.
It's an impossible situation to be in, but I kind of agree with Jack Black's move on this. He can do more good as a Hollywood A-lister for Biden than he can as an "edgy" rock star with a guy nobody's ever heard of.