Just the people to consult about the rights and wrongs of bombing civilians

Yes. Exactly the people to consult on legal and illegal warfare.

You can wail that the Law of Armed Conflict is unfair to terrorist war criminals, but it remains the best set of rules humanity has ever managed to create to reduce the inhumanity of war.

Extremists can not be allowed to win just because they themselves care nothing for the deaths of civilians, cynically hiding behind them and then exploiting their suffering which they are entirely responsible for.