it's tricky.
An 18-year old can be a war hero. An 18-year old can invent Google or win the lottery or cure cancer or do all of these great things.
Why dont we just "let it go" when an 18 year old commits rape or murder? We don't look at the kid at 50 and say "oh, that murder didn't count, he was just a silly 18 year old kid".
Not saying a quote is the same as murder. Just saying it's weird how *some* things at 18 count to define a person, good or bad. But some things do not. If obama said, at age 18, that he plans to one day take over the presidency and install an islamic congress to rule the USA, I doubt most getbiggers would say "eh, it was just him being a silly kid".