Something is bothering me about where the blame is landing in this thread.
When I was nine I knew how to read. I might have had some trouble with Shakespeare, or Bible passages, but things like "Danger", "Warning" and "Caution" were all words I understood. I also listened when my parents told me something like "Be careful", "Don't touch that", or "Go put your goggles on before you go out and play with your friends and the bb-guns".
We don't have the whole story here, but everyone's cast the parents in a horrible light. It wasn't like the Mom just handed her Son a loaded gun, turned around and thought about what colour to paint her bed-room.
Are the parents free of guilt in this situation? Certainly not, but they shouldn't bear the whole blame, and neither should the companies manufacturing and selling the guns.
Parental responsibility can only go so far. Could she have forced her son to wear the goggles, sure, but at some point the child has a judgement-call to make. 'Mom told me to wear them, but I don't like them, they get foggy and itch, so I'm not gonna' Doesn't matter when that call is made, before he goes out or after he's already out there playing, and once he takes them off it's his own damned fault. He was told.
Now you could argue that in that case he shouldn't have been playing airsoft at all, and I agree with you. If the child isn't going to follow the rules, then he or she shouldn't be playing, but you can't pin that all on the parents. I know plently of people that ignore rules they're told explicitly on fields, and all of them are over the age of majority. What does that make them? Morons. What does that make the kid? The same. Is it the parent's fault? Partly, but I don't think it's time to break out the cross and nails for them just yet.