@Nye: You might want to recalibrate your definition of "offense". I'm fully with dneary on this one. If I were session chair of a conference with a formal policy as in this case (which I have been), and one of the session speakers launched into a talk with the correct prediction that "some people may be offended", I'd be angry. Not offended, angry. Also I'd probably be so surprised and flustered that I'd let the speaker proceed anyhow, and then I'd spend the rest of the conference wishing I'd had intervened on the spot. If nothing else, hearing about this incident at least prepares me mentally to exercise responsibility as a session chair more assertively. The case of a keynote speaker deliberately flauting the policy is both more egregious and harder to handle, since there is typically neither a session chair to intervene nor a next speaker to bring on in his place.