Adopted children, when they find out they're different from their parents and feel misunderstood, unappreciated, and alienated, can fantasize that their "real" parents would understand and love them just as they are.
Birthed children, when they find out they're different from their parents, can fantasize that they're adopted.
The lesson here is that most kids at some point feel alienated. It's a normal response to the situation. Doesn't mean a thing about the rights and wrongs of adoption.