I didn't see it as Stuart standing up for himself. Instead it was Stuart being stubborn like a little boy that did not want to do what his mummsy wanted him to.
If Stuart had really stood up to her he would have given her a mature explanation along with his stance. As it was it was a case of. Errr like.......Err like.....I don't know like err. like err.
It will be at least another decade before Stuart can be classified as an adult.....

Or even longer.....