Reverend Hale is a complex figure in the play. He is motivated by an honest interest to help the people of Salem, starting with Betty Parris. However, Hale is clearly also motivated by flattery and pride. He is an expert on witchcraft and the treatment he receives in Salem confirms his high opinion of himself.
As the play goes on, Hale's honesty, his clear-sightedness and his integrity become the most important - and questionable - elements of his character. Hale has helped to stoke a witchcraft paranoia in Salem. When he is confronted with the truth about the accusations made by Abigail and the other girls, Hale is forced to choose between a loyalty to the truth and a loyalty to the majority of the town.
Importantly, the town's position reinforces Hale's initial assessment of the situation in Salem, lending continued credence to his "expertise". When presented with a compelling insight into the true nature of the witchcraft accusations, Hale cannot take an honest view.
...he allows his ideology to hide the evidence presented to his reason.
Abandoning the view that witchcraft is actually taking place to admit that the accusations are a fraud also means that Hale will be admitting that he was wrong, diminishing his personal importance and the importance of his "expertise" on witchcraft.
Hale does ultimately admit to being wrong and comes back to Salem to advocate for Proctor's release. He finds honesty in the end and attempts to win back some integrity.
Hale embodies many of the moral contradictions of the play: he is a man of integrity who, although at times misguided and overzealous, is willing to change his mind when confronted with the truth.