On public buildings and privately owned places, Graffiti destroys and distracts the professionalism of the building. Art should be expressed, But not in a way that hurts others.
Illegal: You are defacing someone else's property. If government owned - same principle - it isn't yours.
Graffiti has the ability to make something ugly beautiful again. Also making graffiti could be considered a way to make a statement. I believe graffiti done right makes the city less grey and boring. I do not however think writing in simple black for no reason other than to write "penis" all over the place is correct. I would place those in concentration camps. (for legal reasons that is a joke. )
cause nobody say you can't do art
It should be legal, But illegal in certain places and without a license. An artist should have express permission from authorities in order to do graffiti, And the artust needs to be verified as having 'decent' art. Graffiti is an art form, And it's harmless as long as it doesn't harm anyone. With that being said, Graffiti should not be legal on buildings, But rather public spaces, Like a main road
It should be legal with the permission of the property owner. In communities that are amenable, There can be designated spaces for graffiti artists to display their work.