There are few things that eight year olds take strongly against; spinach is probably high on the list, followed by haircuts. The Act of Settlement generally figures nowhere in their list of things to be avoided. So when you see a story about a putative cub scout objecting to taking a child's promise to serve the Queen, you just know there's a gobby parent behind it.
The boy himself is quoted as saying "I really enjoy the Cubs and don't want to feel left out or different to everybody else", thereby probably breaking from the script in which his mother had rehearsed him. Just leave the boy to get on with it; he's got a lifetime ahead of him to make up his own mind on such things.