I actually had a friend who actually tours as a musician school me on the whole situation...

He thinks Jack did this to try to save the asses of every road gig worker they employ. There were risks of not being able to get venues insured over it and it put the rest of the shows they were doing at risk of being cancelled anyway due to that. (You can't get a venue insured if they think there's definitely going to be attempted violence, even if that violence doesn't come from your fans but from people who hate you)

As much as I'm behind Kyle all the way, it's correct to admit that he put a lot of people out of a job with a thoughtless joke.

Maybe, just maybe, Jack wasn't just thinking about himself and his safety, but was also thinking about the safety of all the road gig workers employed by Tenacious D. Do they deserve the risk of right wing violence because Kyle made a throwaway joke? Not really. Maybe that's why Jack was so upset about, even, because he understands the Tenacious D tour is a business and with a dumb joke Kyle just wrecked the businesses ability to do business.

Anyway, a small consideration for Jack Black maybe not just doing this to save his own skin and income.