Art comes in many forms, many materials used to express the artists' vision, and many different templates on which an artist can express their vision.
Graffiti is a sensitive subject for some, and depending on the location of the work, and the nature of it changes my acceptance of it. I don't appreciate vulgar destruction of private or public property, there are enough A-holes in the "graffiti" industry, that cast a negative connotation over all the quality artists.
My specific adoration for graffitis come from the places not many venture to, under bridges, tunnels, locations that are actually brought UP, by a little splash of color. These hurt no one, there is no said "destruction" only an artist bringing something new to the table.
From the regular joe, to the Bansky's of the world whom of which put thought, and heart and soul into their work, I truly appreciate, because some folks would pay millions for a black line drawn on a 30"x25" canvas, because of a name,but look down on a true work, because it is on a pillar, under a bridge..