I think this is where we fundamentally disagree. You see it as "if we don't ban allergens, we may as well not ban guns." Which, to me, seems an incredibly specious comparison. I, on the other hand, see it as "if we ban food allergens, why not air-born allergens? Stop teachers from wearing perfumes, due to allergies. Don't allow flowers in the school or on school grounds, due to allergies." Between us, it is a "half full, half empty" argument here...and, let's be honest, neither one of us is likely to change the others minds with this type of argument.
So, let's switch gears. At what point would you recommend that schools should have the authority and/or obligation to ban an allergen? When it is one student affected? 10? 100? If the allergen is a mild irritant? Induces vomiting? Hives? Causes need for an emergency Epipen?
On a tangential, but related, note...
One of the links I provided in the OP mentioned how the peanut allergy is on the rise in the US. So, one must ask the question of "why?" Is this due to an actual increase in true peanut allergies in American kids? Or, is it an increase in false diagnoses? If there is a true, legitimate, proven increase in both number and severity of the allergies (i.e. being in the room with a PB&J sandwich causes anaphylaxis for 1 in 10 kids), then maybe these bans are legitimate. However, if there is no true increase in legitimate numbers and severity, then I have to maintain my stance that school-wide bans on allergens is a hysterical overreaction (and, likely, a preventative measure in our lawsuit happy society) without true base in logic. It seems, at least at this point, to be little more than a "but, think of the children" emotion-laden reaction. After all, how many school children have actually died from peanut allergies in schools in history prior to these bans?
And, finally, to address my earlier point that kids are not the "functional retards" some like to pretend they are, I grew up with a kid who was deathly allergic to bee stings. He carried with him, every day, an emergency Epipen. One was also kept in the teacher's desk drawer and in the school nurse's office. When we were in the second-grade he got stung on the playground. Immediately, his throat started to close up and he couldn't breath. Before the teacher could even get to him, he had already taken out his Epipen and shot himself in the thigh with it, thus restoring his breathing. He was sent to the nurse, and then home for the afternoon. He was young, but still smart enough to know what to do. Kids, especially kids with life-threatening allergic reactions, can very easily be taught what to do and what not to do. There was no need for school-wide bans on recess or open windows, or even a need to ban him from the playground. He knew what to do if he got stung, and he did it. The teachers and nurses knew to keep an eye on him, and they did. Banning things that could potentially put him the presence of bees would have been seen, 25 years ago, as a hysterical overreaction...just as peanut butter bans should be seen as today.