Denying politics is also a mode of oppression. I had a teacher calling women in my class “females” which is very insulting in French as it only ever applies to animals, not peoples. When one of them complained, he dismissed her by saying it was not the place for her feminist militantism.
Another note on Martin Luther King : he said several times that the greatest enemies of black liberation were not the KKK but those (mosty middle class, benefiting indirectly from racism) who saw the problem but advocated innaction because revendication wasn’t polite or there was better problems to adress.
This experiment does not prove that money keeps people more honest than absence of money, but more honest than token exchangeable for money. If a control group was allowed to cheat without receiving money at all they might (my prediction and I would bet a dollar on it if I didn’t use Euros) cheat even less. Then, the hypothesis “money keeps us honest” would be disproved.