Because free public chargers are not for a single user. A 100D takes up to 20hr to charge at a 208v public 30a charger. So the taxpayers in the area need to build one for every >=60kWh car to allow overnight charging. Just the head unit is $10k US plus install, then they run on electricity as well. This is why we can't have nice things. FREE public chargers aren't planned out for overnight parking or they would just install it at your home. But they could certainly help a traveler in something like a Fiat 500e. It charges in 4 hrs. L2 is a 500e's Supercharger. Take a nap while charging and continue on.
Again, it's not right to unplug someones car, but I'd like to hear the WHOLE story. Those who crave FREE, the coupon cannibals, don't have a lot of boundaries when it comes to consideration of others. I'm still convinced by watching the video there is a lot of the story the OP isn't telling. FREE people aren't trustworthy in my experience. They are always the martyrs in every storyline they tell.
Watch what happens next. OP raises a stink with the city. City ignores it. OP threatens lawsuit (a coupon cutter favorite). City removes charger.