YOU are presuming a lot when YOU lecture that all allergic people should be kept behind closed doors and the school should banish any children who interfere with your child's desires. I was NOT lecturing you -- just offering some honest advice through hard earned experience.
Personally I have never heard of a pediatrician who recommended that a child eat no protein but peanut butter. But keep in mind that most MDs had only a week of nutritianal training in Medical School. The wonderful thing about our universe is that there are many forms of delicious and healthy proteins readily available in our food supply. Try your library, or the Internet. You may be amazed! You will also find this same peanut prohibition if you get out and about in other places too. I know a Sunday school near here that designates peanut free zones in their Sunday morning religious programs. Are you suggesting that the minister should just banish all of the peanut-allergic children from church?
What are you going to do if your child DEVELOPS an allergy to peanut butter some day? That happens, you know. Humans develop various allergies throughout their lives, and sometimes they overcome them, as well.