...excessive hatred of Slavs.

This isn't true. Germany's allies during WWII was the most varied ethnic, and some Slavs also fought alongside National Socialism. Just check out some events, like Betrayal of the Cossacks, who were persecuted by the Bolsheviks and Stalin. Cossacks were an important cavalry that was part of the Slavic culture for decades, they fought on the side of National Socialism, against the Soviet Union and Bolsheviks, and were led by a German general, Helmuth Von Pannwitz. Another important figure was the Warlord Serbian, Momčilo Đujić, fought alongside National Socialism, leading the Chetniks against the Partisans.