On the one hand, I can get where he's coming from on a humanitarian viewpoint, that praying for someone else's death is in the abstract a bad thing.
But to break up a band that's been going for like 25 years and that was the foundation of his entire success over something that could be equated to being a jovial quip either means that tenacious d has other issues as a band or that Jack Black has some political opinions that are more important to him than his friends.
I hope he gets a wake up call and attempts to repair the relationship with Kyle Gass as soon as possible.