Jack is very gullible and easy to manipulate if you know what his weakness is. He needs to be a savior. He has to save the damsel in distress, it is his nature. Of course, once he does that he has a connection to her for life. Just as with his wife, he then feels responsible for them. Juliet has been especially set up to have effect on him. She looked like his wife, she is now an outsider like him, and she is marked. So, he projects much of his own feelings into how he views her. Just as Ben knew he would. Even though Jack is gullible, and stubborn and too self righteous to listen to his friends. He will see it clearly soon, and once he does....Juliet better watch her back.