((I've not read the books yet,but reading up about the character and watching the movie, as dark as he is, he doesn't seem interested in really HURTING children, let along killing them. He just does what he does. He seems more violent towards other beings like himself, via that guardians and man in the moon, etc.
Even in the movie, he seemed more interested in taunting the kids than actually attacking them. I actually noticed, when he's talking about the Dark Ages, when he notices the guardians, he sees come kids and bends down for them. To me, he didn't look like he was going to be necessarily scary, but just...acknowledged. I don't even think he was "on the clock" 24/7. So yeah, he could be scary, but the Boogeyman is also a tool to make children behave and be obedient to their parents. Good children normally had nothing to worry about with him, aside from a bad dream once in a while. You want scary...you should read up some of the German tales of the Sandman. He used to pluck out the eyes of naughty children and feed them to his children on the moon LOL. Boogeyman tales are pretty tame by comparison to the Sandman fairy tales...and more practical.))