Addressing students behaviors is necessary for the well being of all students in the class. It is not fair to you or the class to allow an individual who is not following through with the policies of either the class or the institution to continue down a destructive path. whether the infraction is cheating , loud angry outburst or any other act of unprofessionalism, Ignoring the behavior will not result in changes that can be sustained long-term. The obvious impact is that the situation will get worst , sending a message to the other students that the behavior is acceptable or at least tolerated.