I'm 26 years old with a child of my own, yet I deeply crave acceptance from my parents. It's my downfall. I guess we could look at our own offspring. Could they seamlessly shrug our love off when they're older and still be considered healthy, well-rounded individuals? Contrast it with the folks who shrug off OUR love for no longer wanting to be a Witness. Do THEY appear to be well-rounded people?
Craving the love and approval of our parents seems natural to me when I think of it like this: when a stranger walks past me on the street and screams some random profanity at me, I shrug it off and keep walking. Why? Because they don't know me. They don't know who I am and what I stand for. Their opinion is therefore obsolete. But when the people who gave you life, who know exactly who you are and have had a lifetime to make an informed decision of you then REJECT you, deeming you unworthy of love, let alone contact... well. That really smarts.
Perhaps from a Darwinian perspective, we could examine things in this way: being rejected by the very ones who propagated their genes to give birth to you could result in death. This may resonate more strongly with younger Witnesses whose parents shun them. But for older Witnesses who still yearn for their parents to accept and love them, we could think about how natural selection works. Standing out and not going along with the crowd is usually what kills you in more primitive species. It's going along with the crowd of your kind that heightens your chance for survival in the animal kingdom. As ex-Witnesses, we're standing out from the crowd we knew and accepted as our only "sort" growing up. Perhaps we're hard-wired by biology to experience this apprehension to being rejected (and subsequently standing out) because it signals a very real threat to our survival.
I'm purely extrapolating here, but there might be some science to it!