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.
Even simple facts, when learned superficially, can turn against you, for reasons related to representativeness bias. Norbert Schwarz et al. write1: