Vortitude

But it's not self-defense; it's a reliance of them believing a lie. If one was to assault the robber, then they'd have attempted to defend themselves physically, or if they tried to reason with the robber, then they'd have defended themselves in a moralistic fashion, or even fleeing would have been a viable option. Instead, they've chained themselves to a lie, hoping to be believed.

The secondary problem with lying to the robber isn't one of morality, but of slavery. You become his slave, chained to the need for him to believe your lie, and to continue to believe it until your emergency situation is resolved. His belief in your lie creates your ability to defend yourself on the course that you have chosen. The best system is to learn to never rely on a lie. Lies are fragile and flimsy, and require more work to nurture and grow than many alternative paths. In truth, the only people you can successfully lie to are those who trust your word--which, seem the people you'd want to lie to the least.