Do you know the definition of assault? It is any word or action that makes another person logically believe they are in danger of being struck, harmed, or whatever. So yes, violence that frightens customers or coworkers constitutes a form of assault. It doesn't have to progress to the point of battery where you actually punch somebody in order to be deemed gross misconduct.
And I have no doubt been around quite a bit longer than your parents and have been employed for all but a few months since I was 15. Sometime I need to add them all up, but I'm guessing that I've probably drawn a paycheck from 30 or more different kinds of jobs by now--several were held simultaneously. And in not a single one of them from way back then to present, would the behavior you described have been acceptable, tolerated, or not result in termination.
Again, you can't unring that bell. But the next time you can mentally tell yourself that being mad as hell and screaming at somebody are two separate things. You can't control being mad. But you can sure control whether you scream at somebody or not. You can't help being angry. But you can see that hitting a post is something different from being angry and choose not to do that.
All is not lost. The old cliche of that which does not kill us only makes us stronger has an element of truth in it. If you get a handle on this, I see you as being a great human resources manager or some other such professional somewhere on down the line. So get to it.