As distasteful as war is, to do nothing in response is to invite more of the same.
In my dealings with individuals who are driving their own agenda tactically, the tactic they guard against is the tactic they use themselves. They think it is fearful and fear it too.
The tactic they don't find quite so amenable is open handed tactics. Tell them what they are doing and why. They deny it so you explain what they are doing in that respect.
I'm not sure that it has the same efficacy on large groups so the fall-back position is the obvious one. Eye for an eye. As an defensive gambit. Revenge is incedental.