This post on the Kapiti Coast Facebook page has prompted a flurry of responses, nearly all supportive of the girl and condemning this sort of customer:-

Shocked at some people ….
Went to Kena Kena 4 square 15 mins ago. We always get amazing service from all the staff there.
Today there was a young girl in training who in my eyes was doing amazing.
She serves a older gentleman who was soooooo rude to her so she passed him on to the lady in charge who sorts out the problem very quickly and nicely
He then says “you should leave that new girl packing shelves”
To her response ” she can only learn by doing what shes doing”
He then says “not in my bloody time”
I then cant help myself and make a comment on how rude he was as he walks off.
There is actually no need for such rude people. I feel for the poor girl. I went to her as i left and praised her for how well she was doing.

Most people are capable of being provoked by bad behaviour — for example, we have remonstrated on occasion to workmen of the Parkwood property business for making protracted, excessive noise at our boundary, despite a promise that it would not happen again.

However, the sort of thing reported is unnecessary, hurtful and just wrong.  It’s possible this man had experienced a bad day, but there’s no excuse for taking it out on others.  A serious personality disorder can indicate drug abuse, legal or otherwise.   There are lots of suggestions on what to do in the comments, decide for yourself.