The Allies, Axis, and Comintern all committed atrocities in WWII... but atrocities are not a binary state. The firebombing of Dresden doesn't match up to the Final Solution, for example, and not just in scale - the latter was a formal ongoing policy by the government in charge, not 'soldiers run amok against their training'.

It is good, however, to remind any hawk that atrocities are committed by all sides. If you're advocating for war at any time, you must also accept that your own side is going to engage in atrocities to some degree.