No. To your credit, I don't think it is. But very much not to your credit, that's what it sounds like it is, and that's what Miles is hearing. Is it any wonder that he persists? You've told him there's a wall, and you've told him that because of his qualities he simply can't jump over it. It's your right to put a wall there - heaven knows it is, completely and utterly. But you're failing to explain to him why he needs to not go all sapper-explosive on it.