No, advertising unlimited and then complaining when someone truly does use unlimited is not a problem with my mindset, it's a problem with the person who runs the service, if you don't want people to truly use unlimited, don't advertise unlimited.
You must be living in a bubble if you think that's how companies operate.
Saying that someone is an asshole for using an API in a way which clearly should be possible according to the documentation is a very clear sign of that person being a junior developer who don't have actual real world experience of anything except toy projects. Any developer with some years of experience would understand that this would happen and he should not be surprised over it.
It's very possible that no one involved in this is even aware of this issue, so automatically calling them assholes is somewhat incompetent at best.
Water in a lake is also technically free (depending on local laws), do I have to make it clear that inviting millions to take a cup out of it is not a good idea?
This is the internet? If there are a million people around the lake fond of tea then of course you need to tell them that they can't consume all the water. Offering a free service and being upset when people use it is just naive.