Not condoning violence against a fascist is rolling over and letting them get away with fascist shit. I take it you think Brian Thompson deserves sympathy as well?
Regardless of whether Kyle Gass is doing fine, it still reveals either a weak character on Jack Black's part or significant ideological disagreement with my own beliefs. To an extent that I find him much less appealing as an actor or performer.
If violence against a corporate ghoul, fascist, or nazi saves more lives in the long run, it is 100% justified. If Crooks had not missed we'd be living in a much better world right now and far fewer people would be in serious danger.