I'd be fine with it. People are always charging something or other in our restaurant without asking (they sometimes just ask where a plug IS), phones, laptops. Heck, if someone wants to plug in their car for an hour, no problem.
So he plugs in for an hour a week while his kid plays tennis. He likely pays a ridiculous fee for his son to play tennis in the first place, court fees, plus he certainly pays taxes which pay for the school and all its electricity.
Here in Switzerland at the train stations they have free parking spaces for electric cars, including free charging station for each car (you can commute to the train station, charge your car while you go the rest of the way by train, return after work and pick up your fully charged car). No parking fee, no electricity fee.
If you want to make an example of someone using an electric car, make the example positive. Policeman should have patted him on the back and told the whiner at the school who called him to pay more attention to children's education than snooping around wondering who's using an outside outlet for half an hour.
Don't get me wrong, I'm all for fossil fuels when it comes to my beloved F1, but if I didn't have to shop for the hotel and therefore have to own a stupidly large SUV, I would also have an electric car for running around. If you haven't noticed the climate is changing, your head is buried in sand.