(Government) People should understand the importance of rule of law and the danger of conflicts of interest. Some politicians will get away with as much as they can if they think the risks of prosecution or public outcry are low. Examples (fictional and/or real) could be given showing the effects of weak rule of law, including legislative loopholes/capture, and executive aggrandizement.
I agree that this one is very important, though perhaps not so easy to get people to understand or even care about without some foundational knowledge about history and about public choice theory.