Much as I hesitate to argue with my colleague Brian Faughnan on the Obey/Waters fracas... it is possible that she may not be at fault here. Obey's been showing more and more of a temper over the last few years. There was the yelling match that he got into with antiwar protesters in 2007:
See also here.
I don't know if this is going to be an isolated incident, in other words.