How to tell a friend nicely to stop whining?

[caddyshackjack]

A friend of mine from high school (17 years later) still hasn't matured very much in the whole "nobody likes me everybody hates me" type mentality he always has. We live in different states, and connect through social media sites. All of his posts drive people away, and he's very much ok with posting things like "since no one wants to ever hang out with me" or "I guess no one likes losers like me" even in personal messages he does this. When people try to extend a friendly gesture he goes overboard bombarding the person (in person and via social sites) obviously he needs friends but what is a tactful and sensitive way to let him understand that his actions turn people off?