So much for the turn your other cheek thingy...
I do not believe that "turn the other cheek" means "passively stand there and let yourself and your family be killed". I strongly doubt you would find that many people on FR who would go with that.
If somebody slaps me on the cheek, I may respond with "WTF was THAT for?" and try to resolve the issue without escalation. I would not cut off his head and parade it around the neighborhood (in that, I am different from some Muslims). Somebody who shows me he intends to kill me will get a much stronger response.
The Catholic catechism holds that self defense, in the sense of using the minimum force necessary to preserve your life and the lives of those under your protection, is just and proper.