Why did the SS charge some of their own officers with cruelty?

Considering how evil were the men involved in anti-partisan operations, how bad were these men! Of course it should be remembered that Slavs were generally considered only slightly above sub-human. Was racism involved? SS-Oberführer Oskar Dirlewanger commander of the SS-Dirlewanger Brigade, is to this day regarded as the cruelest of all anti-partisan and extermination commanders in WWII.