Well, it certainly is possible for one side to committ more atrocities than another. Look at Rwanda. It was demonstrably planned. We had accurate intelligence that it was deliberate, and the preponderance of atrocity was committed by the Hutu. Regardless of whatever criminal acts the Tutsi RPF had committed beforehand (or since), the Hutu committed a genocide. Legally, ethically, morally, and politically, the Rwandan leadership bore a preponderance of criminal culpability for that as well.

"It Can't Be Just About Us"
--Frank Schnittger, ETian Extraordinaire