It sounds credible to me - not as a facial recognition algorithm you could use on the man on the street, but one that correlates certain styles of Facebook photo with certain political views. If a conservative is more likely to upload a photo of them doing something that directs their attention away from the camera, while a leftist is more likely to stare at the camera with their mouth open in mock surprise (the soyface expression), a facial recognition algorithm can recognise that despite it not strictly being about facial recognition.