Why would you feel sorry for him? It's like being gay, I don't feel sorry for gay people being gay. People are the way they are, if we all accepted everyone in spite of all the differences... oh well, one can dream.
I would feel sorry for him if he couldn't feel love at all... for friends, family, etc... But being asexual does not mean that! And he is probably happy the way he is, so..
I do feel sorry for the girl, though