People say hurtful things about others, under the guise of being "funny" in order to make them feel better about themselves. If this is frequently directed at you, and especially if these "jokes" are in front of other people, I would consider this a form of abuse, as unintentional as it may be. Can you tell him that his frequent belittling of others is offensive to you and impairs you ability to share a trusting relationship with him?