Wherefore Art...

[Leanne]

Cast out the triptychs,   
cast out the saints.  
Cast out the people -- people is not a strong word here -- I feel you're missing an image that makes an impact
that artistry paints.
Away with all nature,
away with all form.
Away with the substance
that once was the norm.
Eschew the censorious,
accept the notorious -- here your meter is lost.  This should be used to pick up the pace and race to the end, but it's stumbling.  I'd suggest "hail the notorious"
and mediocrity victorious, -- same here -- maybe "the middling victorious"
praising as most glorious -- I'd suggest "praised" instead
Now’s artist so pricey and trite -- a little shift here perhaps to "Today's artist: pricey and trite" or something similar, as "now's" isn't quite right
as he squats and strains -- instead, perhaps "he squats and he strains", removing "as", since he's always that, not just when he's in the act of voiding...
voiding multicolored stains -- I'd like a more evocative word than "multicolored" here.  After all, that kind of sounds pretty, like he's an artistic shitter, whereas the implication beforehand is that pretty much anything he produces is going to be beige.
from a rectum far too tight. -- as this end few lines read like a limerick, I feel you need some extra feet here.  What about "from a rectum that's [dismal] and tight" (obviously, suggested adjectives may require improvement...)

I think at some point we've all written a variation on this theme -- at least, those of us who've read enough poetry to realise how ridiculous it is to hold up what is trendy as the one-true-way-that-all-must-hereafter-aspire-to.  In art, as in most things these days, there is a constant need to dumb down, to appeal to the status quo.  Many innovative poets fade into obscurity because they weren't noticed by (or sleeping with) someone in the New Yorker, or didn't go on a talk show, or didn't write about teen angst even though they're 56 and working in an accountancy firm.