I don't thi that's a fair characterization. I think if your child had a classic allergic reaction after a vaccine it would be fairly easy to get a doctor to acknowledge it. I agree it may be more difficult to convince them something more obscure was caused by an allergy, but have you ever tried to convince a doctor that a food allergy or intolerance was causing bad behavior? It's nearly impossible. The two seem pretty comparable, to me.
Here. This is your belief (which of course you are entitled to have!) You may think it's true, but you have not experienced it firsthand. Some mothers have, and they speak out about it. Do you see the criticism they suffer, on this board alone? This crunchy, non-mainstream, alternative board. Think of the criticism they face in real life, where they are the small minority!
Oh, and I do agree with you about food and bad behavior. 110%!!!!!!