When all else fails, blame (someone who once called himself) a Republican.
FNC reports that Bowe is refusing to speak to his father. Maybe al-Bergdahl the elder told him what good guys the Taliban were, and the son found out different after he met them.
5 years in capitivity in a 3rd world country will likely make one appreciate the US; my guess is that Berdahl sees now how his parents were dead wrong in their beliefs. He may never speak to them again.