When you feel like you want to lash out at somebody.
Get aggressive, forget about manners, say it as it is. Ask a provocative question, answer in a passive aggressive tone. Send an irate reply, or no reply at all. Take it public, escalate it, raise the flag.
There is one question you should ask yourself first.
It is often so that, when that emotion takes us, we want to act to get it out, to relieve ourselves, to trade a long-term effect for a short-term boost.
If it is change we want, we have to find a different way.