Over here in Florida just last week a poor guy working in a convenience store was shot and killed by a robber after he had given him the cash register contents with no resistance. The shooting was witnessed by a customer hiding in the store, and that person said the clerk had not resisted.
That was an irrational action by the robber (more so than the robbery itself, seeing as the security camera is as good as a witness as the clerk). I personally believe you can't preemptively prevent all irrational actions by for instance blowing them everyone you confront away. If you can throw a sucker punch and run away, then go ahead. But if you pull a knife and then they pull a knife (or gun) in a standoff, those chances don't sound good to me. I consider that I've got a lot more to lose than the mugger.