Why is Webber in such a foul mood?!
Its quite possible that Webber has been told, in no uncertain terms, who the No.1 driver is and as such, he must drive with that in mind. This means that if Vettel is directly behind him in the race and the team tell him to "conserve fuel", he must allow his team-mate to overtake him.
In effect, he would've been told that he will not receive the backing of the team, should he wish to go for the WDC, unless Vettel is mathematically out of the WDC.
If you were in the above position, would you be depressed?