I think that this misses the point by saying Sheldon did these things to be mean. I think he did them to use what he calls teachable moments in other episodes, because he truly believes that he's always the smartest one in the room, and that it's his job. He's seems a bit smug because he is, and he seems to enjoy things like this, not because he's trying to be mean, but because he's trying to improve people and the world as a whole, like it's his job, which he belives it is, and he takes pride and pleasure in that, not understanding that he's going about it the wrong way sometimes.