My mum and I were discussing something like that a few days ago, except we were talking about taggers and vandals. What compels one to scribble mindlessly on a building more beautiful or at least functional than one's nasty scrawl, or hurt a sculpture or art piece?

I would tend to agree that those who destroy one-of-a-kind art pieces and such should be executed. My logic is, murder is typically punishable by death because we believe humans to be irreplaceable, unique entities. So, if a piece of art is likewise irreplaceable--and what's more, if it actually links us to and reminds us of our heritage and past, and evokes great sentiment, as art often does--then why not execute those who destroy art?
"Gentlemen, the verdict is guilty, on all ten counts of first-degree stupidity. The penalty phase will now begin."--Divine, "Pink Flamingos."

"The strong rule the weak, and the cunning rule over all." HS!