To the initial poster:
First :evaluate ma-ai, check your own ego and then determine the benefits engaging. Often the second step takes care of many problems. Cuz like, wudda you care if he's a jerk.
I agree with your general idea that people ought be prepared for anything: plan for the worst; hope for the best. Sometimes, if it's obvious to the attacker, stepping across the street inspires the chase too though. Sometimes though, it's stupid not to find a quick change in route. When I worked nights in an alley frequented by crack-heads and very very cheap prostitutes (and their pimps), I always looked them in the eye and smiled or gave a respectful nod, depending. But as you can likely attest, with some folks, it's better not to engage in any way.
It really is a lot like dog training. Some dogs need eye contact to establish respect in the pecking order and others take it as a direct challenge of dominance and will respond viciously. It's a combo of science and intuition that relies heavily on basic skills and an ability to adapt mid-stream. And we all make mistakes.