I don't think anyone in their right mind would say that was justifiable, and bloody sunday either come to that.
I find the concept of 'war crimes' odd.
for example the RAF bombed germany cities and their population in the belief that it would help win the war: whether that strategy was the correct one-and there's plenty of evidence and argument to show that it wouldn't is besid the point.
My thoughts relate to the reasoninbg behind an act: for instance thr rape of Nanking. There was no military objective there-the victory had been won, the same with the mass rape of german civilians by thr soviet army, the bengal famine.
The Bengal famine was caused by the Japanese invading Burma and cutting off the rice supply to India.
My your argument it's okay to kill civilians indiscriminantly just as long as there is a political motive. That would make any number of attrocities perfectly okay.