Tours involve a lot of people, ensuring the safety of all of those people is one of the responsibilities of the performers and other decision makers. That is hard to do against a rabid fan base of Trump supporters that Kyle Gass/Tenacious D pissed off.
If Kyle Gass’ comments only affected him or Jack Black then I am sure they would have just ignored the backlash or made a simple apology. His comment didn’t just affect the two of them but everyone who worked on the tour, including the venue employees, promoters and anyone else in their proximity. Putting the livelihood and safety of the people you are responsible for is an entirely different situation than just acquiescing or giving into the MAGA crowd. It is about being responsible with the platform you have and protecting those who may be hurt by how you use that platform.
It sucks it went down the way it did as they clearly aren’t Trump supports but taking responsibility to protect others they care about was an empathetic and responsible thing to do for the thousands of people they put at risk during their international tour as any future concert could have become a target.
Jack Black is not a dumb guy and every thing I have seen or heard of him beforehand gave me the impression that he is a caring and warmhearted person. I can easily see a person like that would make a choice to take the reputational and financial hit to protect his fans safety and wellbeing.
It wasn’t about whether Kyle Gass was right or the fans didn’t agree with it. Kyle Gass and Jack Black didn’t want to gamble the safety of their fans by stepping into a huge ongoing and developing international political quagmire.