Punctuality being a form of respect... I never thought about it that way, but I think I agree with you. It's a powerful definition. Therefore, I think you should unveil that precise wording to your boyfriend (gently, of course). Persuade
him that he should put an effort into being on time by telling him that being so late is disrespectful to you. That is the best way to give him the capability to understand your feelings.
Try giving him your definition of the concept of punctuality.