We're trying to make a point here that the public should be the ones using the public space and not commercial and private interests.
This guy lives in a different world. Equivocation aside, those 'public' spaces are privately owned. When this guy says that the 'public' should be the ones to decide, what he really means is that he thinks his opinion of how the space should be used ought to trump that of the owners who pay to own and maintain their property.
edit: Questions of legality aside, I mean.
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.
some wiki info: http://en.wikipedia.org/wiki/Public_space and http://en.wikipedia.org/wiki/Common_land
Something tells me the "artists" aren't nearly as offending by indie music bands putting their stickers all over every available surface. It's not about principle, it's about hating "the man". Fashion.