The analysis in this paper centres on an email exchange between a lecturer and a student at the University of Auckland which resulted in the dismissal of that lecturer. This dismissal gave rise to significant controversy, both off- and online, as to whether the email itself was simply "intemperate" and "angry", or more seriously "offensive" and "racist". Through a close analysis of the interpretations of the emails by the lecturer and student, as well as online evaluations made on blogs and discussion boards, it becomes apparent that the inherent discursivity of evaluations of impoliteness arises not only from different perceptions of norms, but also from the ways in which commentators position themselves vis-୶is these evaluations. It also emerges that the relative level of discursive dispute is mediated by the technological and situational characteristics of the CMC medium in which these evaluations occurred. It is concluded that research into various forums of online interaction provides a unique window into the inherent variability and argumentativity of perceptions of offensive behaviour, as a public record of discursive disputes surrounding particular alleged violations of norms of appropriateness can be (re)scrutinized in such forums.