Paul Crowley

Although my first comment was slightly tongue in cheek, I'm still not quite sure why "some people are sometimes wrong" is a pre-requisite for "it's okay to tell them so". Apart from anything else, it assumes that it's only okay to tell people that they're wrong if you're right that they're wrong, and actually, I think when two people disagree it's okay for both of them to tell the other that they're wrong, because we (and they) don't know which of them is wrong until a consensus is reached (and possibly not even then, but at that point we have stronger evidence for which view is correct)