What exactly have the Christian Assyrian militias done wrong? Sorry, I'm not doubting your suggestion that this is true, but I just haven't heard anything about them committing war crimes. Do you have a news article for that?
For me the destruction of Hatra and Nimrud are war crimes because they are part and parcel of their ethnic cleansing campaign to wipe out the history of any other people in the region aside from Sunni Arabs. That includes Kurds, Assyrians, Shia Arabs, and even ancient Persian influence (since they especially hate Iran). Despite their lame claims of being iconoclasts and being holier than thou, it's also obvious that they're doing this to cover the fact that they were desperate for cash and looted the treasures of these sites to sell in black markets. A small caveat in the Taliban's 2001 destruction of the 6th-century Bamiyan Buddhas in Afghanistan was a Taliban envoy who basically admitted it was in retaliation for aid money that was sent to restore ancient statues while Afghan people were starving in a famine. This is really all about money and sending cheap political potshots across the bow. That is what makes the destruction of Nimrud and Hatra all the more infuriating.But I agree that history is sacred. The destruction of Hatra is, for me, a war-crime that's as bad as the execution of hundreds because they didn't follow to the letter what ISIS believes is the right interpretation of Islam.