In the case of "stupid" it carries definitions that would support your use of that term in this sense, however it also carries definitions that imply personal insult. For example, Miriam-Webster's first definition of "stupid" is:
"1. a : slow of mind : obtuse."
Over time, the common use of words sometimes tend to gravitate toward a specific meaning. In at least western culture I believe this is the situation with "stupid;" it has gravitated to the common use as being an insulting term, as opposed to an intellectual description.
A stronger example of this gravitation