There's been an ongoing debate on nature vs. nurture for millennia now, and I'm expected to buy the "nurture is everything" side of the story as the absolute truth just because I'm donor conceived and thus expected to? Says who?
I'm sure couples opting for donor insemination like to believe that nurture trumps nature and that the real father and the one who impacts the child more meaningfully is the man raising this child. This is probably how they can arrive at the decision to use donor insemination in the first place. And that's fine.
But who says their offspring are somehow morally bound to subscribe to this idea? Has no one ever heard of children believing in different things than the people who raised them? Atheist children of fundamentalist parents? Traditionally minded children of hippies? Childfree children of the Quiverful movement?
Surely it is not inconceivable that a child raised by people who believe and claim that blood and kinship ties are relatively unimportant can beg to differ! And feel the loss of her real father, according to her definition of fatherhood!
If my father had, say, died before I was born and my mother had, say, married another man who accepted me and supported me, wouldn't I still be entitled to call my real father my real father? And wouldn't I be justified in wanting to at least know his name, his ethnicity, his religion? To see a picture of his? To meet his half of my family tree? To hear stories about him when he was a little boy? Something?
So, what's different about donor insemination? Intent? How does intent change the facts and how is it supposed to change the child's interpretation of the facts, when it was not the child's intent to be fathered by a person not intending to raise her?