It is a common misconception that aggressive venting of anger is beneficial for the person who is experiencing strong outbursts of anger. As if it is a way for a person to release that tension by perhaps visualising themselves hitting the person that has angered them or metaphorically throwing punches at their problems, thus physically exhausting themselves and becoming more rational.
Unfortunately it does not always work like that.
According to research such ways of anger venting creates a link between angry emotions and violence, so in a way it actually does more harm than good. The punching bag confronts such a person by giving presenting a manual for releasing anger. It starts out easily, as if the piece is giving instructions on how to prepare yourself for hitting the target, but gradually it tries to convince the viewer to focus their attention to alternative, more introspective ways of managing anger.