I think the point of the quote is not that young folks are more able to unlearn falsehoods; it's that they haven't learned as many falsehoods as old people, just by virtue of not having been around as long. If you can unlearn falsehoods, you can keep a "young" (falsehood-free) mind.
(Last month's started a little late, I thought I'd bring it back to its original schedule.)
A monthly thread for posting any interesting rationality-related quotes you've seen recently on the Internet, or had stored in your quotesfile for ages.