Probably what I expect most people to do: Realize attacking right now might be suicide and plot their revenge for later when the situation is more favourable/profitable.
OR:
Be ok that your character's story ends with them dying fighting for their cause...which is better than the "eaten by wolves" epitaph on most D&D character's gravestones.
I'm not saying the DM isn't at fault for the way he handled it, but this idea that OP was forced to kill his own character!?! is probably BS.