I remember thinking that about the 16 year olds at the time, but then at the same time I thought given the number of Supernatural stuff marketed to teenagers. Harry Potter, Twilight, Vampire Diaries so on and so forth.
Then again, those kids were captured, tortured, and eaten by those ghouls in short order, that is what set Harry off to the point where he totally lost it. Of course it didn't help that Lasciel's shadow was stoking his rage, but I think even if she wasn't in his head he still would of lost it. What happened to those kids was that horrible.
Was just thinking about this and how the discussion may be too one dimensional. Wizard power is but one power source. The Gatekeeper may be the most dangerous, not because of his wizard capabilities but because of a Mantle he has. The same could be said for any others.
We don't even know what Mantle the Gatekeeper carries, if he carries any. All we know is he traded in one of his eyes for a Nemesis detector made of the same material as the Outer Gates.. We know he can also tell what might happen in the future with it. That is he can see odds, not the future exactly, as in Turn Coat, when Harry was on the boat, Rashid did his eye thing and told Harry what his chances were, then when Harry hopped onto the island, Rashid saw a different future. Mantles also are not the same, Eb and Rashid both call being the Warden of Demonreach a Mantle, yet off the island it has a limit, as in with power boost, the shores of Lake Michigan, beyond which it is merely a title. The mantles of the Queens, Ladies, and Knights seem to have no limit.. However in the case of the Knights, they can numb pain, but not prevent serious injury.