Actually I would say that kids' confidence are slowly destroyed by parents over the years. I think a kid started off with full confidence and curiosity towards life. The trick is to keep this flame alive and not extinguish it.
Yes, I 100% agree with this. Kids are a clean slate, and very curious. They have no reason to have any esteem issues unless someone tells them so or makes them feel bad about themselves.
There will be times when kids get their confidence shattered at school or some other place, but I think the key is to instill in them a sense of love and worth, and let them know that they are wonderful people. It's harder to do than it looks, especially when parents get busy and forget, but supporting them daily will go a long way for them in the future.