I'm not suggesting that raising kids with allergies is easy. But, I am saying that raising those kids is the responsibility of the parent. It is their job to make sure that they teach their children properly, raise them with the proper knowledge, and arm them for what they may encounter when their parents aren't around. Part of that is taking personal responsibility for what they do and don't eat. Personal responsibility seems to be a horrible concept for some people. Why that is, I will never understand.
Teach your kid to eat the lunch you provide. Talk to the kid's teachers and cafeteria workers. Train your child about the consequences and severity of what will happen to them if they eat what they can't. But, don't force other parents to alter their own child's lunch to make sure your kid isn't harmed.
You talk about the plight of the working class, but completely ignore the fact that peanut butter is a reliable, inexpensive, source of protein that many members of the working poor rely on to make sure their child gets at least some nutrition in their lunch. By banning peanut butter in schools, so that Timmy isn't tempted to trade lunches with someone and thus hurt himself, you just robbed Billy of the inexpensive lunch his parents can afford to provide for him. The old saying goes, "my rights end where yours begin." You have the right, as a parent, to feed your child what they can eat. You do not have the right to make sure that other parents remove food from their own children's lunch sacks because you raised a child too stupid to understand "you will die if you eat this."