Never attribute to malice that which can be adequately explained by neglect, ignorance or incompetence.
Stupidity implies it is something that cannot be changed. Usually their behavior could be changed but it is just a hard task to change their behavior that requires the person in question to be willing to change.
I prefer this fuller version
Stupidity implies it is something that cannot be changed. Usually their behavior could be changed but it is just a hard task to change their behavior that requires the person in question to be willing to change.