This board is a nice example of how people deal with cognitive dissonance:
Having taken a stance, they ignore evidence against it and latch on to everything that supports, or at least appears to support it, even if it does not. In politics, in handling investments, etc.
A good example of the old Kahnemann/Tversky thesis that markets are not fully rational - and a big opportunity for those who remain calm and rational to take advantage of gut-driven behavior of others in the market. "Momentum-driven" stock price movements illustrate this, as does behavior of voters.