Should We Clean Up Good Graffiti

I recently underwent a contract to clean up some graffiti on a huge wall outside a primary school. Naturally I was happy to receive a contract such as this so I went out in good spirits looking for the graffiti that needed cleaning up. I was expecting the usual swear words and other such nonsense that teenager seem to have fun writing but I was pleasantly surprised.
    
The graffiti was a true work of art. A picture of someones face with the words "Hazelwood Massive" written in pretty cool writing. It really did look awesome. So as you can imagine when the man told m that is what needed cleaning up I was pretty surprised and it must of shown on my face because he then said, "Apparently it gives the school a bad image."
    
So anyway I carried out my job and got rid of the graffiti but my question to you is "Is good graffiti a problem that needs to be cleaned up or is it an admirable piece of art work that not many people can do?"
   
Go into this topic in more detail at The Green Animal World.