Some of it is really amazing. Some of it is pretty stupid.
I like seeing it on trains, to be honest, but only where they haven't been kept up and are in desperate need of a painting.
On buildings, I don't like it at all, and all of the arguments used in the first couple pages were really week.
Art is art, fine. We can say that grafitti is art, I won't disagree; some of it actually is. Most isn't, but I won't worry about this.
The whole "you're a drug user, drugs are illegal, so you can't criticize other illegal activity because it's illegal" is silly. You don't have to be perfectly straight to object to illegal activity. I would call the cops if I was robbed from.
Drug use does not generally hurt anyone. It's broadly considered a victimless crime.
Graffiti is not a victimless crime. Whoever owns the property is the victim. This is true whether it's a building, car, home, billboard, etc.
Second is the claim that it's okay to paint up a governmental building because we all pay the taxes that buy it. This is nonsense. Because you pay for something doesn't mean you can do whatever you want to it. It's the color it is for a reason. It's not as if the blank wall is somehow offensive and needs to be changed.