Curing cancer sometimes requires it to be cut out. It’s not ethically abhorrent to use deadly force to defend yourself or others from certain deadly force.

That is correct. The evil people you have to defend yourself against are human. If you continue to delude yourself that you are only allowed to fight against that which is not human, and thus all your enemies must not be human, you will fail because of the contradictions inherent to this delusional point of view.

You need to take a principled stance against fascists, that they are fought because of what they choose to do and what their choices require of the rest of us. They aren’t born this way, you can’t find the fascism gene under a microscope, you can’t do phrenology and determine that fascists all have this or that skull shape. They’re just human. If they have to not be human for you to be willing to fight them, you will lose.