Then I agree with what you’re saying. However there is one entity that can rig the market and that is the US Government or its financial surrogates which is not beyond the bounds of possibility.
The difficulty in even the US Government trying to rig that market is: "it is not the only market".
Crude oil and other petroleum products are traded in multiple cities around the world. Greatly restricting or otherwise playing games with one market would only drive the traders to the others, and it would be done in hours if not minutes. All can be reached electronically.