Why do people say turkeys are stupid?

Because turkeys are not very smart. Yes, we should love them a take good care of them, but we can still eat them. As long as we don't eat to many, just enough to keep their population at a reasonable level. This way, the surviving ones have enough food to eat, and their are not so many that there is not enough food for them all and they starve. This rule applies to all animals that we eat.

Anyway, turkeys have about as good of a brain as a chicken. They just are not that smart, but there is nothing wrong with that!