Phil and I have been secretly debating over the last month or so (very slowly, there's only a couple of comments each). I'm not sure if either of us know how much we disagree with each other, so maybe someone else can clarify (click the heading, or follow the link at the bottom).
As in the discussion on Borat, there is a tension between politeness and honesty. Different people can legitimately disagree over where to draw the line between the two.
I think is an interesting question in ethics. A rule utilitarian is concerned with the consequences of his actions and realises that he will seldom be able to predict consequences of his actions. We think that rules like, "don't tell lies' and "keep promises" on average have better consequences than the alternative and so become moral rules to follow unless we have excellent reason to believe that another action will be better.
I argued earlier that profit seeking in a free market is also a moral rule that should generally be followed. Another rule related to don't tell lies is (could be?) "truth seeking". If you are a journalist you can?t have much of an idea what consequences your articles will have. Trying to get at the truth will usually have the best consequences. Same thing goes for a debate or any occasion where differences of opinion are being expressed.
People love talking about the "truth" and the best way about finding the truth is to try and evaluate other arguments critically and honestly and to sincerely and honestly argue your own case, even if you know it might hurt somebody's feelings.