Intelligence, in order to be useful, must be used for something other than defeating itself. Knowledge of human heuristics and biases may cause people to selectively find those biases in arguments they disagree with. This ability to destroy arguments that aren't already accepted will make a more knowledgeable person less able to change their views when presented with evidence.
Public information campaigns that confront myths with facts, or warn people that a given claim is false, necessarily reiterate the information they want to discredit. [...] When the false claims are encountered again on a later occasion, all that is left may be the vague feeling that "I heard something like this before." This sense of familiarity, in turn, will foster the acceptance of statements as true.
- Schwarz, N., Sanna, L.J., Skurnik, I., & Yoon, C. (2007). "Metacognitive experiences and the intricacies of setting people straight: Implications for debiasing and public information campaigns". Advances in Experimental Social Psychology 39: 127-161. (PDF)