What was the "public shaming" of Kino and what was Steinbeck's attitude toward some wealthy people?
Kino could not know it, but he had no chance of selling the pearl for anything close to its actual worth - the buyers had already consulted each other and established their plan to humiliate Kino and discredit his judgement. As the ones holding the power to buy or sell the merchandise, they had control of the encounter, and they used it to reinforce to Kino and all the village that those who hold the power, in wealth or knowledge or status, must be respected and never challenged. Kino's attempts to stand up to the buyers and their false valuations resulted in the villagers questioning not the buyers, but Kino's actions.
"We do know that we are cheated from birth to the overcharge on our coffins. But we survive. You have not defied not the pearl buyers, but the whole structure, the whole way of life, and I am afraid for you."
Steinbeck distrusted organizations and authorities as being corrupt and unconcerned about those whose lives they controlled. The buyers, the priests, the doctors, and the political officials all reflected his interpretation of how they treated the poor and powerless.