There's countless examples of retaliatory protests turned violent or outright attacks after PR disasters. The classic sequence of events is: Assault force takes contact, a couple of 105mm's take care of threat, Taliban claim CIVCAS, weak-minded populace believes Taliban, then protests at local VSP, the ODA there takes fire from TB using protestors as human shields or diversion.
And its not just limited to CIVCAS. You think Abu Ghraib wasn't used as a recruiting tool?
What I think you're driving at is, we haven't gone through what these four guys went through? And you're right, I don't have it as bad as the young marine out on patrol. Im also not debating how war could drive someone to commit this act. However, someone's shitty situation doesn't make them exempt from the tactical directives, ROEs, LOAC, or Geneva conventions.