gnosonarcissism
This word is a combination of "gnosis" (knowledge) and "narcissism" (self-centeredness). So, gnosonarcissism is a self-centered view that one's level of knowledge is correct and/or complete despite what others know. This implies a lack of understanding that others might know more in areas of knowledge in either a horizontal way (breadth of knowledge) or a vertical way (depth of knowledge).
Because of his gnosonarcissism, he was unable to believe that the ideas of others could ever be better than his own ideas.