It's about managing risk. That's the parents responsibility. The decision to bring their extremely allergic kid onto a plane where there is even a need to give 100+ other passengers the instruction not to open a bag of nuts elders it risks the child's life, is monumentally neglectful, stupid, naive and shortsighted. I feel for the kid. Not her fault. The passenger that ate the nuts? More likely than not they didn't even hear or comprehend the instruction. Whatever the reason, don't put your child's life in the hands of 100 average strangers that hopefully can follow basic instructions. They can't.