My little bro is a chronic whiner!?

My little bro is a whiner, or at least that is how he presents himself in the few on line communities we belong to. He is single and wants a girlfriend but is going about it the wrong way. I have tried to kindly boost his negative feelings reflected in his posts with upbeat, positive feedback but his indirect response to my advice (just be yourself - stop trying so hard) was to go and F* myself. How do I tell him in a non-threatening way that he needs to project himself as less negative and more confident (not arrogant) and not post about every minor injustice that he encounters on a daily basis?