One wonders what the "on guard' muppet was doing at the beginning of the conversation. If he had been truly monitoring and listening he would have been aware what was going on. To jump in at the latter stages with such an unsympathetic comment and lack of understanding would be enough to cause some 'bleeps' on the radio frequency. I might start with," pilot calling 'on guard' please identify yourself." They would not know if you were ATC or not. You might just get a response to allow an ID and when it's all over you can make a targeted comment.