Fascism will exterminate itself. It's an auto-cannibalistic ideology.
To the Nazi mind, society is like the rings on a tree with the "pure" and "deserving" being at the core. The outer most layer will always be the "other" and the "enemy". So as each enemy is defeated, the field narrows until the end where they'd be two Nazis left trying to kill each other.
Viewed in this light, anti-Fascist skull crushing is benevolent.