Progress has always been bought with blood, violence is the only motivator that is actually universally respected, and these Nazis don't have the same distaste for violence you do. If they reach certain numbers they begin using violence to try and control politics. That has to be actively discouraged to minimize violence, which means people with certain tendencies have to motivated to not be Nazis. The only universally respected motivator is violence, the threat of force is how all governments in the world maintain order. Less violence is needed to prevent the spread of Nazi beliefs than would be created by Nazi beliefs unchecked.

This modern idea that there is no such thing as moral violence is a lie and a tactic. Ignore it and forget it. Violence is a tool. Misusing it is evil. Using it properly, it kills evils.