Also, you cannot use Rasho's championships with the Spurs as credible validation without pointing out that Nazr Mohammed beat him out for the starting job the year that he won. Regardless of that, pretty much ANY big man (i.e. Nazr, Rasho, Oberto) who lines up next to Tim Duncan looks like a defensive stalwart. Just check their defensive ratings before and after Duncan.
That said, Bargnani seems to be practically un-coachable. He is too thin skinned to accept criticism. And he is just good enough at a few things to make him blind to the things he is horrible at.