Looking at the world in a different way
As a teacher, when children climb and stand on things in the classroom you tell them to get down because it isn't safe. There is that fear of "Oh noooo he/she is going to fall, then I have to hear it from the parents etc., etc., etc...." You know a big part of your job is to keep the children safe and make sure they aren't hurt.
As a parent of a toddler, you see them climbing and the first thing you do is grab your camera and record this next step in the growing process. Ok, yes I don't want him to fall and get hurt, but at the same time I'm not really worried that he will. Now I do not encourage him climbing up on things that are not made for climbing, but know that it is all part of the learning process. I do find myself having to ask him to sit down a lot after he has climbed up, but the climbing doesn't bother me.
When Blake was learning to walk I took the position of... yep he's going to fall. Yes, he is going to be ok. Richard and I decided early on that the best way to deal with him falling was to tell him he was ok, give him a hug if needed and send him on his way. People are always in shock when he falls, gets up and goes on. If he does cry, all he needs is a little bit of comfort and he's on his way again.
I guess in some aspects it's the same for climbing. I would rather him try and get hurt than be afraid to try at all!