How dare you judge the beliefs of religious people. I respect both parties. The Son, for living his path, and the parents for living theirs. Everyone makes choices.
All "US admirer" does is post anti-haredi/orthodox posts.
He or she is just a basic anti-semite, soft-sell version.
I have ceased communicating with him or responding to his posts or threads.
(And I say this as a person who left an Orthodox community.)
There is a difference between respect for others right to have a position you cannot reconcile YOURSELF to and total ostracism of your own family members because of those differences.
There is no indication from the story that "David" sought to change the views of his parents or preach to them to come to his view. He seems to have respected their right to continue the orthodox view he left. They should have done the same for him. Nothing was advanced or changed by that ostracism, other than many years of hurt feelings.
I have a Jehovah's Witness sister. She could not be further from everyone else in the family on religious matters. We (all her seven siblings and our families) continue to have good relations with her. I am glad we do.