I think intent comes into the definition of plagiarism. He should take a fall over that, but intent is difficult to prove.
He should get a job there he is qualified for - changing the perfume in the bathroom dispensers.
He's done it enough, in both print and his own artwork, to show it wasn't just a one-time accident. When you rip off someone's art, that is pretty hard to claim that you simply came up with a similar concept with similar wording.
"...Ward Churchill would do himself some good to express a profound apology to people he has offended and misled.
He should also come clean about his appropriated American Indian identity. "
Sometimes it is. Sometimes it isn't.
Churchill sold artwork depicting a line of Indians riding over a hill. This is a mirrored image in virtually every detail of another person's work. Much as fingerprints are identified by matching a minimum number of points of agreement, this artwork lends itself to the same process.
There are no points of disagreement between the two pieces of art, and many, many dozens of points of agreement. This did not happen by accident. No reasonable person would find that a claim of originality on Churchill's part could in any way be justified. The man is clearly a fraud and those who support him are parties to the fraud.