I see what you mean and I do realize it was trying to remain true to the source material. But it wasn't just that one instance. There is a line between outlining the horrors of pedophilia, and engaging in it.

I recommend you watch it again with this in mind, and you will see there was quite a few scenes early on where the movie is unnecessarily sexualizing the kids (even getting shots of their body).

I personally don't think there's any excuse for that, and even worse this is the toned down version where originally the horrible sexualization was more explicit.