Appeasement is not defusing. Brilliant and concise. Kudos!
In the scenario outlined, the apology should have been to the lady bumped and, when the "punk" started to get into the face of the bumper, the response might better have been, "I apologized to her, as I bumped her, not you. Have a nice day," and leave. Done calmly and with a coolness, this can often get the blusterer to back off.
Humor can also sometimes deal with a situation like this as well. Something like a LOUD pleading, "Please don't hurt me, Sir!! I apologized! HONEST!!! Don't hurt me!!"
In a mall, as was described, such an action and comment tends to catch the eye(s) of those around the area, including LEO's and Security. They take a dim view of someone threatening someone else.

Some folks around will laugh AT the guy doing the verbal assault, some will back away and Security will come forward to assess the situation. Not a bad response.
Or the Commander Ivanova response: "Don't. You are too young to experience that much pain." Which could, obviously, cause the situation to escalate, but would make HIM throw the first punch. From there, it's self defense.

Some options for the scenario, submitted with seriousness and a little tongue in cheek as well...
Lee Darrow, C.Ht.