The sheriff is a snake eating its own tail. He is power seeking power, a greed that can never be sated. The contest is pointless. There is no winner. The same act is repeated over and over again until the Doctor summarily ends it. This Doctor has no patience for going through the motions. He does not want to play games. He finds his goal and takes the most expedient steps necessary to reach it. The robots represent mindless oppression. They will only ever be an external force. They are focused on a goal yet they will feel no joy if it is reached. They are a void that can never be filled. They are not dead they are nothing. The Doctor accepts that death is necessary. Death is not outside of life it is an intrinsic part of it. Death gives life meaning. The robots exercise power but they will never be empowered. They will never be more. Their destruction is meaningless.