that may be "proper" in your opinion, but a President commuting and lowering a potential prison sentence does not mean that he believes it was too harsh. Commutations and pardons can happen for any reason, or no reason at all. It is fully at his discretion. How you personally choose to interpret the meaning and motive for it is up to you. That doesn't make it so.
It definitely acts as a message to all Democrats that they have carte blanche to do whatever they want and break ever law.