I think this whole situation is rather consistent from an RP perspective:
You have a member of a guild doing as he wishes, regardless of perceived arrangements/treaties/etc
The council of that guild chooses to do nothing about it, therefore offering tacit approval of the action(s)
In char, this is really easy to understand. That other Neidar do not want to be painted with this brush is their prerogative, but why would the rest of the donut, *in character*, not believe this is the policy of the guild? If the guild membership is so upset about it, why not a coup? Maybe an ambush of the renegade element?
If, in character, others felt this was the way the Neidar was going to be operating then it would seem that attacks against any Neidar would be appropriate.
There are lots of possibilities here!
As a side note, I applaud Manglor's in char response. It would be easy to email councils of other guilds and say "Hey, you guys know that's Irk and I'm not a part of it", but instead his departure says (to me anyway) that "I don't like where this guild is heading so I am going to leave."
As for Irk, I think his char should behave however he wants and deal with whatever the consequences. And to be fair to him, that's exactly what I have seen from him. His behavior after his death was completely in char from what I have seen from him without a bit of OOC complaining.
Finally, all guilds should support assassination as a means to electing a new leader.