I think most people understand where it is and isn't appropriate to draw graffiti. Wherever there are blank walls, I don't see much of a problem with graffiti if it improves aesthetics (not if it's just random gibberish). In this case, the person that did this probably did not care at all about the world around him (akin to people littering). It is so obvious that this wooden arc is not the right place to graffiti, and I'm sure most actual street artists would not do anything to this landmark.I still don't think it will do a hill of beans to stop the blight of problematic tagging. An issue that likely started when our ancestors learned how to paint on cave walls and what not. And marking seems to be an overall issue with the mammal line of vertebrates outside of that. So really, good luck with that.