Of course blame is assigned only to the manufacturer, if the manufacturer does not notify the consumer of a hazard that is well known to them and could be easily avoided if the consumer were made aware.
Just curious, what method would you suggest would have worked in making someone who ate two bags of microwave popcorn daily for ten years aware of this astoundingly tiny danger? A marching band waiving banners stating that he is a stupid idiot? Because some tiny text on the box wouldn't have affected this case in the slightest.
You CAN'T make laws or regulations or rules based upon exceptions. Is it possible to get this 'popcorn lung' from casual consumption of this product? I've yet to see any credible evidence about it. The two class actions based upon it were thrown out of court. This was simply listening to a sob story without using the slightest bit of common sense - yeah, you got sick because you didn't use a product in a rational manner. That's your problem, not anyone else's.
Then again, rational reactions and acceptance of personal responsibility have slowly slipped away from even conservative forums.