How do you convince someone the person they're in love with isn't interested in them?

I work as a kind of dating advisor for this website, and I often get people giving me this classic situation: I love this girl, but she says she just wants to be friends. How do I make her fall in love with me?

Usually, somewhere in there is something about how the girl either just got out of a relationship with a jerk, or is interested in a jerk. Often, these people have been pining over the same girl for months, even years.

From what they tell me, it's obvious that the girl has little to no romantic feelings for the guy, and that she just sees him as a friend. But when i've tried to convey this, the guy usually gets upset or huffy.

Anyone have any ideas as to how to get through to a guy like this? How can you get a guy to see past his emotions and realize that she's just not interested?How do you convince someone the person they're in love with isn't interested in them?
Yes, let them realize their love is singular, meaning they are holding on to the feelings they have for the person, not the person. As wierd as this may sound to some, yes even love can be selfish, it's not that you actually want that other person, it's more like going through withdraws from that great feeling, and if you let them go it's cold turkey time. If there was only a love patch :) People do turn on and off at different times so there is always the ';chance'; that the other person will awaken from that not feeling anything for you, but more than likely your always in this futile battle against yourself when you end up on the giving end and with no reciever, and no give back.How do you convince someone the person they're in love with isn't interested in them?
forget it, people won't believe until they fet hit.