I think that as a general rule, a singer's lyrics are his/her deal. It's much more personal (for a good artist) than a bass line or guitar riff. So, when I was the singer of a band, I got really offended and hurt when my bandmates challenged my lyrics. However, being a little older now, I think that it's a singer's job to make the decision on fight or flee. If you really have a problem with his lyrics, confront it and prepare to lose him.
Okay, so that was general. Specific to this situation...I'm with you. No reason to be a jerk and diss other bands. That kind of hate is just ridiculous and as hate and aggression are much more contagious than peace and love, you gotta stay away from that junk.
