I really don't understand the view that he's selling out or conforming by shaving it off.
Unfortunately people do judge others and dismiss them based on their looks. I feel a lot in the house do (Lisa in particular) and judging by that poll it seems many viewers have too. At the end of the day it's just facial hair and if removing it allows others to give him a chance and actually see and appreciate his personality then I think that's a good thing.
It's obvious David doesn't like the fact that the others have already written him off. It's clearly causing him anguish, enough to bring it up at dinner. If making a statement like this can help a few of them give him a chance or help the public see past the beard to his personality then I think it can only be a good thing. Like Tim said, a beard won't win him Big Brother, and I'm sure David himself would like the public to get to know his personality rather than just be known as the guy with the ugly beard.
In a perfect world everyone would treat everyone the same regardless of what they looked like, but unfortunately that isn't the case. David's not an idiot. If he feels that making a statement by simply shaving off some facial hair will help his chances with and others and in the game (especially if the suggestion came from an outsider and past BB winner) then of course he should try it. I don't think that makes him a sell out at all. Just someone proving that they want to be there enough to make a statement and sacrifice some facial hair.