While it may be counter productive to call someone else stupid, we cannot ignore the existence of stupidity all together. So what is stupidity? What does it mean to be stupid? I propose stupidity comes in 3 forms.

No one has the right to tell me what I should or should not value and I have no right to tell anyone else what they should or should not value. That said, I as stupid those who have no idea what it is they truly value. “The unexamined life is not worth living” Socrates/Plato.

Among those who have a reasonably clear idea of what they value, I consider stupid anyone whose goals are clearly inconsistent with those values.

Finally, there are those who have a clear idea of what they value and set reasonable goals or define reasonable problems bases on those goals but pursue counter-productive strategies.