Art, Truth, & Bull, SHE confronts Fearlessly
It seems to me your objection is more to a type of activity that presents itself as art, that is recognized as art, but because of the intent behind it is more of a political product than actual political art. You mentioned the term propaganda, which I agree no more deserves to be called art than advertising. And the analogy is pretty clear - you sell an idea rather than a product but your aim is never more than instrumental. So, I agree art can’t be purely instrumental in its aims; it can’t merely be the case of selling an idea external to itself. That doesn’t mean, however, that the idea internal to the art, that which it expresses, as in the horror of war in
Guernica, can’t be primary. Picasso is not selling an anti-war message, he's revealing one in a unique way - the idea is primary but it works in harmony with the form. So, I don’t think that the idea being primary is the issue here; the idea must in a sense always be primary, but it must work within the expression such that it reveals rather than merely commands. And what it reveals must be of value. Picasso does this, Banksy does this, Orwell does this, etc.
The creative act, for instance, in it's pure form is not primarily a process of reason; it's kinetic. I pick up an instrument and begin playing, I feel the pressure of the brush on the canvass, and suddenly, the ideas come. IF the result happens to be political, I have no problem. But an artist who begins from a political perspective is just making propaganda, not art. — Noble Dust
As I mentioned above, I agree that if the motivation is to sell an idea - instrumental reason - then you don’t get art - the artistic potential gets crushed under the jackboot of ideology. However, the impetus for art may be anything including the political. It doesn't have to be a case that it just happens.
Guernica was painted in response to the bombing of the town of the same name. It wasn't entirely spontaneous. That the pressure that pushes the artist's fingers to the keyboard, or hand to the chisel, or paintbrush across the canvas is a wonder, fear, or disgust of a political nature no more negates the final product than any other impetus as long as the art speaks for itself, has its own voice, and is not merely an echo of some prevailing wind that its creator wishes to amplify.