Historically, regular troops have always been sensitive about guerillas: it's like they're not playing fair. Soldiers take casualties from guerilla traps much harder than the same losses to the other side's regular forces. And one of their common responses is to start slaughtering the locals, on the basis that some of them have probably been supporting the guerillas, so let's just kill them all and let God sort it out.
From the guerillas' point of view, this is an ideal response, since it greatly increases the general hostility to the invaders. Which is one reason, leaving aside all moral considerations, why intelligent commanders try to prevent abuse of civillians. Stupid commanders imagine that terrorising the locals will make them more co-operative. Historically, this rarely works.