Let him learn. He is still young and as mentioned new to the dating game. He does sound a little naive, but he will figure it out or at least should. I think eventually he will come to the realisation he has rather high standards and expectations. I can see why you are concerned but I think he needs to discover this on his own. As a friend though perhaps you can help to dust himself off when he falls. You sound like a good friend with a big heart. Sometimes though, like a child of our own, we cannot helicopter over those we closely care about.