I certainly wouldn't label Cera's dad an idiot or stupid in general. But there are many cases where his stubbornness and racism drive him into actions which are stupid even though we might """excuse""" them with his racism. Gee, I never thought anything in the world could ever be "excused" with racism :blink:
An excuse to wear tall pointy white hats perhaps
As for the differences between the two words
Idiot is like a class or category, a label for a person with a low IQ
Stupid is very often used to discribe something.. like "Wow, that's so mind bogingly stupid!" or "It cant be any more stupider than that!"
you cant say "It cant be any more idiot'er than that" =P