Barring all the moral issues or the huge pickle he just put his university and peers in, I'm distressed that a scientist would do this in front of students. Presumably several of these students are planning to study this field and have just watched probably the central authority figure on the subject in their eyes - a point a Psych Prof should definitely be aware of I'd think - decide on the spot with no need, to engage in what amounts to them to be an experiment involving human beings. Because what we definitely don't need are any scientists, particularly those that work with humans, having anything that reinforces any tendency to ever make off the cuff decisions when there's no need to have done so which may also visibly involve doing something many people would object to.

Proper Response: "An interesting suggestion, let me consider it"

If the demonstrators were okay with it then, they will probably be okay with it later, and they also deserve time to reflect on it,a nd if they decide not, then that would be for the best. He could then consult with a couple of his colleagues to make sure this was a good idea and properly consider how best to present the material to minimize any potential problems and maximize the educational value of the demonstration, and to discuss the various issues involved in such a decisions with his students, which would also have valuable educational worth, as it would be a great chance to discuss the importance of giving due and thorough consideration to such decisions. The last thing we need are any psychologists out there who might approach experimenting on humans with anything but the most grave and responsible attitude and considered approach.

So, very unprofessional in my opinion.