You're overthinking this and causing some kind of weird double negative. You're asking for active user input - in order to *de*select - what the user *doesn't* want. That is a very confusing anti-pattern.

Just have the user actively select what they want to avoid from a plain list (no pre-checked boxes).

> Select the proteins you want to avoid:
> 
> [_] Beef
> 
> [_] Chicken
> 
> [_] Pork