And that other thing may well be a problem for someone. In that case we should not serve them anything because of umpteen unknown possibilities that could go wrong. If you are old enough to be flying on a plane and eating the food on a plane then you are most certainly old enough to have been in contact with sufficient food and oils etc for your parents or yourself to know whether you have an allergy or not. Stopping people from smoking on a plane which has a direct evidence base to show it does cause harm is one thing - stopping people eating peanuts which has no evidence base whatsoever is just stupid. Not that I really give a stuff pistachios are far nicer.
I guess I wouldn't be stopping anyone, I'd just serve something else that was less likely to be an issue (or failing that and although not saving anyone's health, better for my fingers, make the bags easier to open).