Michelangelo was commissioned to paint the Sistine Chapel. The School of Athens was commissioned by Pope Julius II. You'll find that a massive number of famous art pieces were commissioned, and I don't think you'll find any serious people who think less of them because of it.
Art and the freedom of art have often been used to critise society.
Now if art becomes a product, where is the critical function of art? Critical art is part of healthy and diverse society, without we're one step closer to an orwellian utopia.
You're tapping into a single category of art -- art that is critical of society -- as if that's the only purpose of art.
The purpose of and the person who commissioned the piece of art is just part of the context and history of the piece. It says nothing of its impact and importance.
My main point is that the commoditization of art should not be detrimental to its critical purposes.
Artists should not be forced to create art that makes money happy.