I don't buy that interpretation. That is, I'm willing to believe that's how your university interprets the regulations, but I personally think it's perverse and unethical when applied to this situation.
When you deliberately deceive someone in order to obtain information that you think they would be otherwise unwilling to give you, the response you get back is as much "about" their behavior in response to your deception as it is about the subject of your inquiry. (And if the researchers in this case didn't think the deception would make their targets more willing to cooperate, why the threatening language?)
That doesn't necessarily mean this kind of research should never be allowed, but it should definitely go through an IRB's oversight.
When you deliberately deceive someone in order to obtain information that you think they would be otherwise unwilling to give you, the response you get back is as much "about" their behavior in response to your deception as it is about the subject of your inquiry. (And if the researchers in this case didn't think the deception would make their targets more willing to cooperate, why the threatening language?)
That doesn't necessarily mean this kind of research should never be allowed, but it should definitely go through an IRB's oversight.