Then you must accept that he is not rational, because he is in fact doing this.
He doesn't share your values. That's how he sleeps. And he may well hate himself (people who treat other people badly usually do) but he doesn't have to feel the pain of that if he indulges in sex and mind-altering substances. He feels no consequences from his actions, externally or internally. After all, this is not the first time he has behaved this way with you, and yet it has never been anything but reasonable to expect that you will be back for more.