It's PC to talk about bullies being inherently cowardly, and suffering from self-esteem issues.
No one is arguing some of these punks are legitimately tough. After all, they spend most of their time fighting off "Mama Bubba" and lifting weights while living at the expense of the state. All anyone is suggesting that flight is a possibility.
As for being prepared to go the distance, I don't think anyone is suggesting they would shoot one, then stop and see what the others do. We've ALL been taught in our respective CWP classes, "Shoot until the threat is negated."
However, most people, no matter how tough, would not go (unarmed) up against a gun, no matter how many there are. You drill one dead center then cycle to the next one and I can pretty much guarantee he's gonna take a long think about his next action. Muscle doesn't compare to bullets and staring into a muzzle is intimidating to anyone.
Your point IS taken, though. ALWAYS be prepared to go all the way.