It's an amalgam of various fears. They include women, rejection, intimacy, and there may even be a little fear of acceptance in there too. Like, if he actually did find someone that would accept him, his brain would boil from the paranoia of trying not to screw it up.
It happens to people sometimes. Usually it revolves around self-esteem issues or maybe some past experiences, or both. My reccomendation is start on the platonic side of things, to a degree, and just try to find a few females in close proximity to yourself that you can share casual conversation with. You might luck out and hit it off with someone.