What Hamilton did was perfectly ok regarding his own race (as in managing his car/tires), but it was also a dick move towards Rosberg. Hamilton was in a win/win situation: either Rosberg would attack him and ruin his tires in the process, or Vettel would catch Rosberg and make him lose pace and points. Other than screwing up, Hamilton could not lose in this situation. I personally am not a big fan of such behavior, but it seems you don't become world champion by being nice to everyone.
The only potential issue I could see is that if Hamilton would have screwed up big time and lose half a lap (big spin, punctured tire, whatever...) and Rosberg would already have ruined his tires by attacking him, Vettel would have been right there to easily take the win. If Hamilton and Rosberg would have driven away from the pack with the pace they were capable of, they would have had a much more comfortable lead over the rest of the pack. So Rosberg is right in saying that it wasn't exactly a team decision.