Yeah, he actually did: http://www.rollingstone.com/music/news/q-a-green-days-mike-dirnt-on-billie-joe-armstrongs-recovery-20130301#ixzz2MJBoTt1s
Q: What was going through your mind as you saw Billie lose it on stage?
A: You know, truth be told, I agreed with what he said, outside of mentioning anybody else. I know that's not Billie. But the bigger side of it – I actually agreed with the rant. But I was watching my friend and going, "You're out of your fucking mind."