Why does this fear of bloodguilt not affect their decision to allow a child to die?
Beccause dying by refusing a blood transfusion is rewarded with praise by Watchtower, while using blood to save a life is still disparaged. They have tried to give an out by allowing fractions, but people have been taught to fear and loath transfusions for years, they will not always adopt more lenient guidelines out of irrational fear. They have also effectively taught people to fear making indecent decisions based on their own conscience, instead looking to the Watchtower for decide for them.
I believe they really don't have a problem with using blood but are afraid to admit they were wrong, they would rather see people continue to die. Talk about blood guilt!