Earlier quoted context omitted.
If you dive into the graffiti scene a bit you will start to appreciate all those graffitis. The story behind some of them is super interesting. There is a lot of "competition", "collaboration", and group dynamics involved. It is truly fascinating. I was living in Cologne (Ehrenfeld) for a while in a place with awesome graffiti and every weekend there were people taking pictures "collecting" and documenting the graffi…
There is exactly nothing about defacing public infrastructure which elicits the tiniest spark of "admiration" or "interest" in me. If you want to live out your "artistic ambitions" do it somewhere away from public property.
Could you imagine that one person's "defaced" is another person's "finally some colors"?
The destruction of property, trespassing etc. is obviously on the wrong side of the law, but on purely aesthetical terms this could be argued either way making it for that narrow category a subjective thing. Proponents of graffiti could argue you cannot deface a faceless thing, opponents would argue they like their lawn short, their fence white, the sky blue. One persons order is another persons prison.
Note that I tried to look at the aesthetic question while ignoring the legal question — mainly because you made an aesthetic argument. For many people the two would be entangled however: Something being illegal makes them look at the result unfavourable, even if a similar legal wall mural would strike them as aesthetically superior to the 10 years weathered white wall that it was before.
As an art person I really see truly good graffiti, yet I have to notice that heavily graffitied parts of my city are tourist magnets — so many people tend to like those "defaced" walls.