I don’t see it the way you do. Don’t you claim that this man has a responsibility for this child. He doesn’t. Its not his child. The one who has that responsibility is the father. He is not the father.
He’s just the poor guy who got cheated on and used in the worst way by the ho of a wife. If he wants to raise the kid as his that’s one thing. If he doesn’t feel as though he can bear to be around the visible reminder his wife cheated on him and used him in this way, I understand.
The ones to be mad at here are the cheating wife and the man she had a child with and who has not taken responsibility for that child.
Under American law, if the couple is married, then the child is legally the responsibility of the husband, blood or not.
Surely there is a third way; such as the father taking the child home and finding a legal adoption agency or some kind of social service agency for the child, rather than tossing him like trash. It's not the child's fault.