Never said they were "dumb" either.
I'm just saying that they don't have the same kind of intelligence humans have, or they would have been behaving differently when their environment changed.
That certain types of whales are very smart in their own way is fairly obvious, particularly smaller species like dolphins and killer whales. Killer whales never became major commercial hunting targets for humans, or maybe we might have seen something interesting develop.
Check out Old Tom.
A more thorough and thoughtful article on Old Tom here.