It’s a good personal policy you have and I’m sorry you had to deal with that individual at that point in time.
Being in service takes an amazing amount of patience and tolerance with people, people whose only contact with you is them exhibiting their worst behavior.
I’ve often heard it said that everybody should get mandatory military service.
I don’t know if that’s true, but what I *can* suggest as a requirement for anybody entering adult life is:
Mandatory customer service.
It works wonders.