This guy seems so full of hatred and criticism, what causes this in a person?

Probably not the best person to be around, I have some friends whom are always negative, but they need me to give them a push of hope, that life is ok and that everything will be ok in the end. He sounds like he has allot of issues to work out of his system. Just ignore him, if he likes you, he'll come around. If hes being rude to you, and is disrespecting your person, the best thing to do is tell him how you feel and that he will never find anyone, and will die lonely, and no one will remember him.