That was a pretty callous way of putting things. It's a rather bold (and entirely incorrect) assumption to think that a child was given up for adoption because the birth mother or parents simply "didn't want" the child.
Sometimes, parents give up their children for adoption because they know they can't provide for the child, and want the child to live a good life. Others are forced by their parents to give up their children (in cases of unwed mothers, or even rape). So the reasons for it vary greatly. And from what I know, for the most part, the decision to give up a child for adoption is a very difficult one for the parents.
I for one don't question the decision of my birth parents to give me up. They could have terminated the pregnancy, and I wouldn't be here today. I thank them for the chance they gave me to become part of the extraordinary family I have now.