I doubt he had a lot of interaction with the Duke community. D-1 basketball is a full time gig. So he absolutely could set a good example for a small number of people inside his immediate sphere of influence. And he was always going to be one and done...so it's really just about what will that one year mean for the rest of your life.
On the other hand, if you are a BYU alum you are attached to the faith. Every time the graphic goes up saying "BYU" the thought is "Oh yea, Jabari is a Mormon." When it goes up and says Duke...the conversation likely goes to Coach K not the unique story of an African American from Chicago who chose lily white BYU...