As You may know, in case you are able to think, most of us learn by watching others doing something, that we repeat to have a notion of learning. In School, what we read maybe will be recorded in Memory and with that, a choice come within. In society, mainly with people who didn't develop, or self control or self irony, we may wish to block any inapropriate comment, just because someone can react without thinking. Therefor, the 3 Wise Monkeys, are wise in that perspective of denying to save in memory what can be evil and with it, become the Evil that was expressed as some content that "we must learn".
If you imagine how is to born in a society in War, if that war takes more than 10 years and you still alive, you probably already saw many Evil acts from random people and therefor there is a temptation to repeat what you are able to see, even if that action is Evil. The same for example to a situation where you may ear about someone who did something that is not appropriate and you may take an action without thinking, based on what you ear or see.
Again, if the people around you are unable to control their own self against any verbal expression, Evil talks can create a rejection and a reaction, that will be more Evil than the Words pronounced. We can see in History, that people use "cute and soft" words, to conquer others, while the choices made by those who spoke cute and soft words, were not soft and cute, but agressive and violent.
Some curiosities about the contradictory reality. For example, most people who like Heavy Metal, are peaceful, while most of the people that like Country music, are not peaceful. This is a global generalization that can be true and false, depending on the Geographic Zones and cultures, but we can see more violence from people who like popular music, than from people who likes non-popular music. The "Non-Evil" can hide some Evilness while the expression of Evil can hide some goodness, which sometimes make sense, because is a way to create "defenses" and "protect" something deeper.
So, Mizaru can deny to see something, because by accepting to see, this monkey can become the expression of the Evilness that it is denying to see. Kikazaru can deny to ear something, because by accepting to ear, this monkey can be unfair and evil against others, based on what he is able to ear and Iwazaru can deny to talk, because by accepting to talk, this monkey can become a target of those who cannot control themselfs, in the confrontation of something else, that can be true or false, while what matters is the self control of each, that he cannot control it.
This is a good reason to deny seeing, earing or talking anything that can be seen as Evil, while not all Evilness is Evil, but what explain reality, while talking about what is not, is like ignoring the Ugly of reality, which is necessary to understand to deal better with it.
There are several interpretations that can be positive about this 3 monkeys, even if what they do can be negative.
For all examples, the "Evil" person could be arrested by those who talk about the "Evilness" that, this person did, while that have another risk, that is well known in reality. "Those who did speak what they shouldn't, against someone with 'Power'". Normally in some countries, Speaking or listening the Evil, can bring us some trouble and life is already a big trouble, so is better to deny to deal more, mainly when is not a subject of study, but third-party choices. What each do Behind the Scenes.