If belief in evolutionary theory made us demonstrably behave worse, should we protect people from learning about it? If a factually incorrect religious belief made us behave better, should we encourage it? A strict interpretation of utilitarianism suggests so.
However, there is no convincing evidence that believing in evolution has negative consequences or that being religious has positive consequences. Actually, I can’t think of any belief that’s both true and clearly dangerous, or any belief that’s incorrect and clearly beneficial. That’s not to say that nothing positive ever comes out of erroneous beliefs. That’s different from claiming that the expected utility of erroneous beliefs is positive. It’s like playing the roulette: you may have a winning streak, but in the long term, you lose.
Things could be otherwise, and I’m grateful that they are not. There is no terrible knowledge, no repugnant dilemmas, no terrible choice between truth and goodness.
Nehaveigur 