A Just Civil War?

Caleb Carr writes in the Washington Post on the justice of an Iraqi Civil War.

Mr. Carr seems to ignore the fact that punishing (on a mass scale)
the whole Sunni Community (including women and children, who inevitably get the worst treatment during war) for the actions of an elite of Baathists
and foreign fighters is prima facie unjust. Surely he wouldn't say
that it is just to target American civilians for the grossly unjust
actions of US officials and corporations? Why should the standard of
justice be lower for Iraqi Sunnis? Raping a Sunni woman because some
Baathist raped your sister is nothing more than injustice. Invading a
Sunni home and killing the people inside because a Baathist did so to
your family is nothing more than injustice. They are practices of
collective punishment that are wisely prohibited under international law.