haha. Not even close. I'm just demonstrating how arbitrary your argument is. Your argument boils down to "I am the parent and I want to have 100% control always til X age" and when I show how the position is obviously ridiculous with some examples (something you agree is ridiculous) you've realized you have no legs to stand on.
You're trying to argue that the child must do anything you want (less physical abuse) until they turn 18 (this age can change by law).
What you don't seem to acknowledge is that we can, as a society, have a graduated scale. We can say that you're responsible until 18, however, we will allow the child to make some medical decisions on their own starting at 14, more at 16. We'll allow them to consent to sexual activities at 15. We'll allow them to acquire a drivers license at 16. Etc.
There is no reason why there must be a single line. We can establish numerous lines where parents relinquish responsibility so long as there is a valid justification for it.
You have no argument against this at all. However, if you wish to argue that the age of 12 is too young for this and it should be 14 or 16, that's an argument that could have merit.