Yup, it is obvious he's cointelpro. He mentions how relevant Gulf of Tonkin is, or how the newly released JFK documents are intriguing but when asked a simple, straight forward question about 9/11 he double speaks. His body language tells it all. After stumbling with his words he managed to stutter out the possibility of Saudi involvement then seemed to develop a slight paralysis of his throat and stammered and yammered about possible other states, while itching his chest and pulling at his collar, but could not bring himself to say more on the issue only to say it was 'no longer so important' as there were more recent events requiring our attention.

The elephant in the room could have shat on his head but he would pretend not to notice it, but maybe blink a lot...

Either, he was nervous in answering that question out of fear or nervous in revealing himself as a cointelpro. If you learn micro-expressions Assange clearly is hiding something.