Statistically, it is overwhelmingly likely that anyone making such a demand of me will be someone far larger and stronger (the vast majority of folks committing strongarm or armed robbery are young males, a group of which an even more vast majority are a lot bigger than a shrimp like me). Even if they are not displaying a weapon and are in fact unarmed, they are making an obvious implied threat of physical violence. Any physical conflict with someone with such an enormous advantage in size and weight has a significant probability of resulting in death or serious physical injury to me. It is not necessary for their threat of violence to be explicit under swuch circumstances. The implicit threat is not just plausible, it's the most reasonable interpretation of their intent.
I am under no moral obligation to assume that they will eschew violence against me, even if they state that this is the case. Their credibility is non-existent (they're committing a felony crime, ferchrissakes...). Scenarios such at this end in serious injury or death to the victims - even non-resisting ones - with sufficient frequency that it is by no means "paranoid" (as Hoyt rather vacuously described it) to be concerned about such an outcome.
Sorry, the implicit threat of violence contained in the act of attempting an armed or strongarm robbery is sufficient moral grounds for violent resistance. I will never even consider obeying any law that attempts to dictate otherwise.