Yes. It is safe to let a 9-year old ride the subway. It’s smart to let him do so if you think he can manage it. The hysterical fear that permeates american culture and determines so many social interactions and manners (parents driving their kids up the block for a playdate, GPS tracking devices on kids, etc.) is pathetic.
Good grief, look at the poll at the Today show: 51 percent say they would not let their kid go, because “[…] Even if I trust my child, who knows how many crazies there are out there?” You’re the crazy out there, moron. Sure it’ll be scary the first time, and yes, there are risks out there for your kid to face. But what are you going to do — keep your child in a padded cell forever?