Anyone who glorifies graffiti needs to answer one question: If your home were tagged during the night without your consent, would you welcome the new addition to your décor or would you immediately call a painter, if not the police?
No institution that has celebrated graffiti in recent years — like the Museum of Contemporary Art in Los Angeles or the Museum of the City of New York — would allow its own premises to be defaced for even one minute. Graffiti is something that one celebrates, if one is juvenile enough to do so, when it shows up on someone else's property but never on one's own.
The question “When does graffiti become art?” is meaningless. Graffiti is always vandalism. By definition it is committed without permission on another person's property, in an adolescent display of entitlement. Whether particular viewers find any given piece of graffiti artistically compelling is irrelevant. Graffiti's most salient characteristic is that it is a crime.
John Lindsay, the progressive New York politician who served as mayor from 1966 to 1973, declared war on graffiti in 1972. He understood that graffiti signaled that informal social controls and law enforcement had broken down in New York's public spaces, making them vulnerable to even greater levels of disorder and law-breaking. A 2008 study from the Netherlands has shown that physical disorder and vandalism have a contagious effect, confirming the "broken windows theory."
There is nothing “progressive” about allowing public amenities to be defaced by graffiti; anyone who can avoid a graffiti-bombed park or commercial thoroughfare will do so, since tagging shows that an area is dominated by vandals who may be involved in other crimes as well.
New York's conquest of subway graffiti in the late 1980s was the first sign in decades that the city was still governable; that triumph over lawlessness paved the way for the urban renaissance that followed.
Original Source: http://www.nytimes.com/roomfordebate/2014/07/11/when-does-graffiti-become-art/graffiti-is-always-vandalism