I don't consider Shaq or Garnett to be "Greats". They were freakishly blessed with talent and very good. Neither had any sort of loyalty to anything or anyone.
LeBron will go down in history as a great but also has loyalty to nothing or at least at the time of his decision did not. There is time to change that perception of him.
Drexler was loyal to Portland for 12 or so years. It wasn't until the FO decided not to continue to surround him with talent and to rebuild, that Clyde asked to go elsewhere. I don't have any problem with that.