Graffiti - Pure Artistic Expression?

The following graffiti chain is transcribed from a men's room wall. It is not known if the person who started the chain ever went back to see if his instruction to "DISCUSS" was ever followed:

I would call writing on bathroom walls a perverse and pathetic form of rebellion...maybe that is a good definition of contemporary art, come to think of it.

The writer defines art as images made for "critical acclaim" or "financial reward". That is much too narrow a definition. Other purposes are personal satisfaction, experiment, transcendental meaning, societal commentary, hegemonic support, and political protest. None of these need involve critical acclaim or money.

It is only in the absence of ulterior motives that we can perceive pure beauty (i.e., art for art's sake rather than for political, selfish, monetary or other agendas). Returning a lost wallet to its owner and then accepting a "reward" does not diminish the virtue of the good deed but surely if that person would not have returned the wallet but for the reward their claim to virtue is less robust than someone who returns it solely because it is the right thing to do.

Tolstoy, among others, believed art needed to reflect high morality to be great art...but if a serial killer made great, creative, and original art, that was based on or grew out of his killing, one could hardly call that art moral..but it could still be great art, made solely from some kind of artistic urge on the part of the killer/artist.

Even if a work of art (or a sunset) seems beautiful to the observer how can we label it "beautiful" unless perceived in a disinterested way (i.e. without sentimentality or reference to anything outside itself)?