I hope it doesn't turn their anger against Ayu as well.
I don't understand why they'd become angry at his response, either, but I suppose it's just because they're distraught and disappointed, and they want someone to blame. That their favorite group broke up of their own volition isn't what they want to hear right now, because they don't want to accept the end of Tohoshinki (heck, neither do I!
).