I usually handle difficult customer interactions in a calming way, by letting them know that they have a right to feel the way they do, even if it's out of hand, but say it to ensure that I understand them and will do everything that I can to make sure they don't stay in a negative attitude and try to provide what they came for, but if that doesn't work and they are persistent into making the situation worse by either name calling or trying to get physical, then that's when I have to bring in management.