@PegasusReturns you have reminded me...
In my daughter's primary school there was a lovely retired teacher that used to give Drama classes for free to the upper classes. These classes were popular and every year a little Christmas pageant would be put on locally that was very successful.
One particular class was very challenging.... because of the parents. Lots of PFB's and seriously entitled parents who were a bunch of complainers.
One of the most vocal in the class was very put out when her daughter wasn't picked for the lead.
Kicked up a big fuss and apparently was quite rude to the teacher.
Drama teacher sent a note home the following day informing all parents that due to the abuse she had received from a particular parent, the pageant would now be cancelled.
She would not be spoken to like that by anyone, particularly when giving up her time. She had the full support of the Principal.
Now everyone knew who had behaved badly, it was the talk of the place. A lot of parents felt it was very unfair as 29 other children were being penalized. The children were upset too. She didn't back down.
That class did the pageant the following year without a murmur.
What I can tell you is that the word was out there that she wouldn't be messed with and she has continued those classes to this day.
Personally I think she was right. She'd had enough, and she certainly put manners on the parent involved, who was mortified that her awful behaviour had been so publicly called out.
Unfortunately for some parents, they neglect to realise when someone is doing them and their children a favour, donating their time, and imagine they can speak to them in anyway they choose.