The claim (P) was that "For all intents and purposes, people of age 16 are not much different from other adults except in that they don't have much experience in life," with the implication that (Q) "therefore they should be treated the same." If P, then Q. I'm saying P is not true. I did not say that !P is enough to say !Q.
While I personally have concluded !Q, there is more to it than what I have brought up - but that was not my purpose in the post. I wanted to point out a false statement because it was being used to conclude something.
"For all intents and purposes" sort of already implies something along the lines of "ignoring the obvious differences, etc" in the same way that 30 year olds and 50 year olds are both adults despite the age difference.
That was not what I meant in my original reply. Teenagers' brains are different from that of an adult - different in a way that a 30-year-old and a 50-year-olds brains are not different.
So, to be clear, the original claim was that teenagers are adults minus the experience. That claim is demonstrably not true. See http://www.npr.org/templates/story/story.php?storyId=1241194... or any other story that pops up when you Google "teenage brains."
While I personally have concluded !Q, there is more to it than what I have brought up - but that was not my purpose in the post. I wanted to point out a false statement because it was being used to conclude something.