Take your cue on violence from non-Christians: Luther

On Governmental Authority, 1523.

You ask whether a Christian too may bear the temporal sword and punish the wicked, since Christ’s words, “Do not resist evil,” are so clear and definitive. [Therefore some teach that] you cannot bear it among Christians or hold it over them, for they don’t need it. The question, therefore, must be referred to the other group, the non-Christians, whether you may bear it there in a Christian manner. [They say it’s] very beneficial and essential for the whole world and for your neighbor.

Therefore, if you see that there is a lack of hangmen, constables, judges, lords, or princes, and you find that you are qualified, you should offer your services and seek the position, that the essential governmental authority may not be despised and become enfeebled [weakened] or perish.