It's about the intention. Banksy's intention was to create art. The other guy's intention was to destroy.
You can see art in destruction if you want, but the guy's intention clearly was to vandalize.
Same reason why Jackson Pollock's pieces sell for millions and I couldn't sell the stain in my garage for a dollar. Even though one could see art in that stain (just like one can see art in nature) having a car with a leaky exhaust doesn't make me an artist.
Destruction is a huge part of street art. No one expects their piece to be permanent. There is a loose code as to when it is acceptable to go over someones piece and a good one can stand for a long time but it won't be there unsullied forever.
These throw ups are making a real statement and it is this:
Banksy is no longer a street artist. He's chosen to give that up by selling out and his work is worth less than a shitty throw up to those in the scene.
You can see art in destruction if you want, but the guy's intention clearly was to vandalize.
Same reason why Jackson Pollock's pieces sell for millions and I couldn't sell the stain in my garage for a dollar. Even though one could see art in that stain (just like one can see art in nature) having a car with a leaky exhaust doesn't make me an artist.