Uhm.
Your general points about racism are correct. People being racist towards an entire culture are backwards and ignorant and have no place in polite society.
Your specifics are way off, however.
First off,
Inframan is not a South Korean film. It was made in Hong Kong, and is filmed in Mandarin. Which is a dialect of Chinese.
Inframan is historically significant, in fact, for being the first Chinese superhero on film. So, you're wrong. The character and the film are Chinese. Someone saying that it's Chinese isn't making a broad assumption that is ignorant of the different nationalities and ethnicities in the continent of Asia - they're actually being precise.
(Support:
IMDB,
Wikipedia)
Secondly, referring to the main character as stupid does not have to mean that the person was making a broad assumption about the character's race as a whole. The main character in
Inframan is, in fact, not the brightest bulb on the Christmas tree. This doesn't mean all Chinese people are dumb, any more than the fact that Jack Burton in
Big Trouble in Little China being a flaming idiot means all Americans are dumb, or any more than the fact that the character of Benny in
The Mummy means all people of Arabic decent are dumb.
Sometimes a cigar is just a cigar.
(And for the record, my Sister in Law is Chinese.)