Yeah, suddenly getting the Child Killer perk and not knowing why would suck.
Especially since everyone treats you like a bastard if you have that trait.

Full disclosure? I've never seen this. For one thing, I never play Fallout without the little darling chill'uns running around. They're terrified of me whether I'm wearing a vault suit or Brotherhood T-51b Power Armor, but I love them so. They remind me the wasteland is a misnomer, that it is vibrant and alive.
With rats.
So no, I've never experienced this myself. My sole knowledge of this is indirect, from a few lines complaining about precisely what CthulusSpy noted, on the TVTropes website. I tend to be very careful about firing automatic weapons*, especially in town.

* Though I do tend to go Rambo on supermutants in the late game. It's oddly satisfying to cut supermutants in half with a minigun.

It's so ridiculous how crazy people get about violence against virtual children. Kill virtual adults in interesting and crazy ways? Wow, that sounds like perfectly acceptable fun for the 16+ crowd! Oh no, you can kill a virtual child in your video game? That is simply evil and your game will not get released!

But people make decisions based on emotion, not logic.

Logic tells us it's only pixels with an on-off cycle (refresh rate) of 30 to 120 Hz. So many pixels, blinking out for ALL TIME...in between refreshes. Someone needs to make a mod that makes those pixels blink in a pattern that will surely win the sympathy olympics. Colorful, religious, disabled, gender-indeterminate, social justice warrior pixels! MIGHTY!