I’ve never met Gaiman, but I’ve met more than my fair share of predatory humans. And most of them were either charismatic or unassuming. They’d evolved social “masks” to enable them to get closer to their prey.
So, don’t beat yourself up if you didn’t see it coming. (I certainly didn’t.)
The question is, as was raised, how do you handle interacting with your memories of unveiled predators, especially when they’ve created things you enjoy.
Personally, I don’t have a problem with enjoying the same stuff I did before, though some of it may be less beloved after the dark revelations. Engaging with their newer stuff is more problematic. Typically, I might be completist regarding things I’m part of the way through, but might not engage with completely new projects.