Graffiti is the art of writing or drawing on a wall. Wall paintings existed since ancient times. I think that graffiti is a kind of art. Many public walls or other surfaces of public buildings are decorated with graffiti.
Graffiti is recognized as a forum of Public art, in many countries painting on public property without permission is legal and could be punished as a crime.
My opinion is that when people use paints, colors and fantasy they make art. But they have to respect the property of other people and of force they can’t express their political views in public locations.
Sometimes a graffiti artist chooses to hide his identity and expresses his views undercover. I think that this is not good because art is something beautiful and nobody can’t use it without accepting the responsibility.