What is the origin of the phrase "Can you say...? where it is filled in with a notion (usually with a hint of sarcasm) the speaker already has of the situation. i.e. "Can you say inbreeding? (The speaker thinks the person in question is an idiot)
I suppose it might be connected to the fact that, nowadays - because of political correctness - there are lots of things we 'cannot' say! For example, you are not supposed to say someone else is 'short'...the correct description is 'vertically challenged'. It's all utter nonsense, of course.
I think it comes from a series of Saturday Night Live skits in the late 70s or early 80s and is a play off of Sesame Street. An adult character in Sesame Street would ask children to pronounce a word. The children would all-together say the word and the adult character would praise them with "I knew you could." or "That's very goooood!" Sesame Street stopped that practice when the parody of their show became a wide spread joke.