The Rebel,
Because humans are an irrational, un-evolved species typically driven or led by their emotions, and emotions are the lowest rung on our socio-evolutionary ladder. Confirmation bias and pride are two of the primary factors, and both have everything to do with emotions and nothing to do with rational thought.
From Wiki: "Confirmation bias is the tendency to search for, interpret, favor, and recall information in a way that confirms one's beliefs or hypotheses, while giving disproportionately less consideration to alternative possibilities. The effect is stronger for emotionally charged issues and for deeply entrenched beliefs (the only thing required to Believe is to Feel - DJS). People also tend to interpret ambiguous evidence as supporting their existing position (i.e. conspiracy theorists - DJS). Biased research, interpretation and memory have been invoked to explain attitude polarization (when a disagreement becomes more extreme even though the different parties are exposed to the same evidence), belief perseverance (when beliefs persist after the evidence for them is shown to be false), the irrational primacy effect (a greater reliance on information encountered early in a series) and illusory correlation (when people falsely perceive an association between two events or situations).