You said you had only conjecture. In any case, why worry about what a church says? What does your Bible say?
At Mt 5:38,39 Jesus said, "You have heard how it was said: Eye for eye and tooth for tooth. But I say this to you: offer no resistance to the wicked. On the contrary, if anyone hits* you on the right cheek, offer him the other as well."
There's one answer: No action.
That of course is considered cowardly, like the man at Isa 53:7,8. Never mind that now.
We can also take his words as caution against retaliation, so common today. This also usually leads to escalation, an unchristian act. We're peacemakers. The apostles understood this. Rom 12:17-21; 1Pet 3:9. A slap on the cheek isn't a serious blow, but it is insulting. A footnote at 5:39 says "The Gospel does not forbid reasonable defense against unjust aggression", and then cites Jesus' own behavior at Jn 18:22 et seq.
As to your scenario, we have answered such attacks by running away, although that often proves impossible. As in the case of Catholic mobs who assaulted us in Quebec back in DuPlessis' regime. In that case, we take a beating.
The standard for taking a life belongs to Jehovah only. In the past he occasionally delegated that to his own people [cf. Jos 6], but not always [cf. 2 Kings 19:35].
This is a principle, not merely a rule or a law. Rev 4:11 says, "You are worthy, our Lord and God, to receive glory and honour and power, for you made the whole universe ..." Cf. Gen 2:7. Remember Cosby's line about his Dad?
So, we don't have permission for defense "(even by the use of deadly force) in some circumstances." I might pick up a 2x4 in defense of an attack, but if my blow kills, I'm in trouble with Jehovah. Especially since he went to some trouble these last 30 years to teach me that he will take care of everything at its time [Rev 16:16], and that only his government can do that [Mt 6:9,10]. Yours cannot. Better to run. Our history is full of examples of these scriptural behaviors.
And, if we die? That's what resurrection is for.
* The Gk for "hit" is the same as that at Jn 18:22, where the NJB has "slap". "Strike" and "give a blow" are also used.