> For virtually all of recorded history by 20-21 you were an adult. If people had no common sense by that age they would be dead.
There is a pretty gigantic difference between "isn't fully developed" and "doesn't exist at all". Try not completely rewriting the position you are responding to just so you have something laughably easy to rebut.
This is particularly silly in a medium where the original you are responding to is readily available, and even more silly when you quote the bit you are radically rewriting in your own response.