wall scribbling

I was walking down the stairs at 188 today and saw that someone had made a stupid scribble on the clean green wall. It made me think of an old saying I’d heard:
It’s easier to destroy than to build.
In your blog answer the following questions:
1) What does this mean? someone is a idiot
2) Where have you seen this happening? never
3) Why is it important to fight against this? so the school stays clean