My friend has a son like that and she also refuses to throw him out. She says she wouldn't throw a dog out how can she throw her own flesh and blood out.
This worthless kid has caused her so much grief. He has no sense of pride. My friend is divorced so it's her decision alone. Alex gets a job and then keeps it for a week or so. Everyone tells her to kick him out and hopefully she will come to her senses. Maybe talking to a therapist is the answer for you. Otherwise fights with this kid could ruin your marriage. Hubby needs to grow a backbone.
He is not doing this kid any favors, because this is not how the real world works. The sooner a person learns that the better. Perhaps your son is depressed, I would go the therapy route, and if hubby refuses to go, just go yourself for your own piece of mind. Best of luck.