IMO:

Is there message they are trying to get across (that isn’t just “Fuck you”, etc.) and how much skill is displayed in the transmittance of their message?

There’s also the valid opinion of anyone that owns the structure, but at the same time if the surface is easily interacted with by anyone simply walking down the street, the public can also argue for their ownership of the public facing part of the structure.

Also spray painting the anarchy symbol on a historic statues face is really shitty, but of course that will happen because of what it represents. At the same time it’s somewhat easy to do with not much skill…

It’s about time.