If you haven't shown in a showmanship class in years, then you may not be up to the current trends. In which case, there isn't much reason in arguing with people who are currently competing in showmanship at the breed shows.
Looking back over your shoulder should not be done. Looking at the judge as s/he dismisses you from inspection is fine, but you should never look back while leaving a pattern. If you would like to see this added to the AQHA rulebook, feel free to submit a rule change proposal.