Just tell him that.

I can guarantee you that he's either already heard it from others or thought the same himself.  Maybe it will be enough hearing it from you to get his act together, but I doubt it.

I had this same situation occur for me, and thankfully I realized it after the first occurrence and came to my own senses.  Unfortunately it sticks with you and that is something that you have to live with and keep it as a personal life lesson.  But not all lessons are easily learned.  And not all people learn the first time.