I have been saying these things for years. Parents protect their children too much. Kids need to take risks, and they need to get hurt when they make mistakes -- both physically and emotionally. Parents shouldn't inflict pain on their kids, but they should let the kids take chances, fall and skin their knees, and deal with the consequences.
This article does a great job of laying these facts out in a very persuasive way. I highly recommend this for any parent or anyone who has influence on a parent.