Mencius thought that virtue was a matter to be developed while Xunzi felt that what was required was not development, but reshaping. The first is like a sprout coming out in a tree whereas the second is like a piece of wood being shaped into an object required by humans. (Chinese Philosophy) Apart from the argument as to whether goodness comes to man from birth or the state, man should practice goodness according to both the philosophers. In those days, living in a state was for the benefit of the state, and this philosophy certainly benefited the state. The general acceptance among them was also that men could be good if they chose to and it did not matter from where this came - birth or inclination. The difference was in thoughts as to where this morality originated from - Mencius believed that it came from the heart and not through enforcement by the state. According to his beliefs, the inherent quality of any child is to be good and men have only got to carry that forward. On the other hand, Xunzi felt that the state has to control behavior of men and decide what principles needed to be enforced within the state. These are needed for the development and survival of the state, and certainly this viewpoint is more practical. His point can be put as saying that humans have to wait for a teacher before becoming correct in terms of behavior as also for observation of the principles of rituals. This is because of the nature of men being essentially evil. (Xunzi (Hsun Tzu) (310-220 BCE?))

This teacher will be thus a representative of the state, and his teachings are in common interest. The good instincts highlighted by Xunzi are of courtesy in relationships and the ability of controlling one's own desires and instincts. This has to be pushed ahead by the state, as these are not natural. The knowledge of the rituals of behavior will lead to orderly behavior by men. When men do not understand needed principles, the behavior of individuals will continue to be wild and irresponsible. This happens as he feels that humans are essentially evil, unlike Mencius. At the same time, this explanation is quite close to...

It is clear that desire is the main reason for evil nature in men. This is also the view of Xunzi, and when this desire becomes unlimited, and then the state will suffer. This will also act against morality. In the present days, such a person will end up being a criminal. (Plutschow, Xunzi and the Ancient Chinese Philosophical Debate on Human Nature)
At the same time, he believes that the lives of people should be on the basis of natural harmonies and regularities, and this is quite different from both Mencius and neo-Confucians. This behavior is also not against the workings of Heaven, and here should not be efforts to try that. When efforts like that are made, it upsets the balance of the triad and that will lead to trouble. This view can be seen as agreeing with the views of Confucius who agnostic about spirituality and concentrated on humans concentrating their efforts on human matters. (Xunzi and the Confucian answer to Titanism) Thus one can see agreements in the philosophy of the three as also disagreements.