Thanks for posting that. Not one to complain about blogspam, but that's one of the all-time great "internet motherfucker" posts. Neither Sciencegeekgirl.com (lol, brand yourself harder) nor anyone else can do much to add to it.
They may not be stupid, but that's pretty much the definition of ignorance.
The interesting part is the discussion of what these wrong mental models look like and how you can teach a correct one.
Absolutely. There was much they did not know, as is true of anyone. "Ignorant" is not an insult, it simply means you do not know something. Would you say Aristotle and Newton knew everything about everything? If not, then they would be, by definition, ignorant of the things they did not know.
By modern standards, absolutely.
By your definition they're ignorant, but not stupid?