He's relying on a law made made by men (customary rules of inheritance) to govern God's blessings (or curses). Who does he think God is, the CEO of a corporation? 
15. And God said unto Abraham, As for Sarai thy wife, thou shalt not call her name Sarai, but Sarah shall her name be.
16. And I will bless her, and give thee a son also of her: yea, I will bless her, and she shall be a mother of nations; kings of people shall be of her.
17. Then Abraham fell upon his face, and laughed, and said in his heart, Shall a child be born unto him that is a hundred years old? and shall Sarah, that is ninety years old, bear?
18. And Abraham said unto God, O that Ish'ma-el might live before thee!
19. And God said, Sarah thy wife shall bear thee a son indeed; and thou shalt call his name Isaac: and I will establish my covenant with him for an everlasting covenant, and with his seed after him.
20. And as for Ish'ma-el, I have heard thee: Behold, I have blessed him, and will make him fruitful, and will multiply him exceedingly; twelve princes shall he beget, and I will make him a great nation.
21. But my covenant will I establish with Isaac, which Sarah shall bear unto thee at this set time in the next year.
The professor is either ignorant or a lyin' sack.
That says it all. The promises went to Jacob/Israel, then to ALL 12 of his Sons.
He's relying on a law made made by men (customary rules of inheritance) to govern God's blessings (or curses). Who does he think God is, the CEO of a corporation?