Re: Offensive "art" deserves an offensive response.
Simple rule of thumb I use. If you have to argue the case for something being "art", it almost certainly isn't.
I know someone who sees literally no value in "art", and thus classes all non-engineering, primarily aesthetic works as "a waste of time". If you were talking to them, your rule of thumb would define nothing as art. Which is certainly true from their point of view, but not necessarily from others.
Full disclosure: I think this particular piece is indeed a waste of time, but I'll defend the creator's right to call it art, and defend their right to claim any defacement is vandalism.