If you are making money by breaking the law and annoying people then I have far less sympathy for them than if their legal private property where damaged. IMO, It falls under the category of destroying illegal campaign advertising on public land.

Again, the original postings weren't allowed (like spam to my inbox).

There are some who argue that billboards are like noise pollution, but with your visual instead of auditory space. I think that is partially correct, and so I don't mind this kind of corrective action.

Note that this kind of of public art display is exactly what makes NYC a vibrant place to live and other areas really boring. That kind of vibrancy definitely has economic value.