Shacknews has published a very thorough four-page BioShock interview with lead designer Ken Levine. Most of the interview focuses on the storyline, so a spoiler warning is definitely in order. Since I don't want to quote anything spoilerish, here's a bit about the child-killing controversy, as it applies to both BioShock and Fallout 3:
Shack: What went into toning down the Little Sister harvesting sequence and keeping you from killing them outright?
Ken Levine: I think a lot of people on the boards were upset when they heard you couldn't shoot the Little Sisters. I'm not sure why, but that's their prerogative. I thought it was much more powerful to have it right in front of you, with that choice. I still find that sequence almost unwatchable. If that's tame, I don't know... I mean, I guess people are accustomed to different things.
Shack: There's been a similar outcry among certain Fallout fans, with Bethesda undecided about killing children in Fallout 3.
Ken Levine: Sure, same thing. It's every developer's call. I personally believe that art is art and reality is reality, but it wasn't meaningful in our game and it didn't advance what we were trying to do. There were gameplay problems with it, and it was just the wrong thing for us. At the end of the day, it was a controversial decision internally, with people asking, "Well, are you limiting what people can do?" For me it was a no brainer--well, not a no brainer, but it was a clear path once I thought about it.