It goes as far as to compare the "highly probabilistic predictions" of psychology to those of quantum physics, and it even cites Richard Feynman. It's just laughable.
In one instance it uses the word "stochastological".
I'd also suggest that one of the reasons people perceive the study of human behaviour as unscientific is that it so frequently is.
Studies of human behaviour are inextricably bound up in politics. Many studies are designed, whether consciously or unconsciously on the part of the authors, to advance the authors' own political or social agenda.
Even if you avoid that problem, many studies are just plain statistically lousy, and employ deeply non-random samples.
And finally you've got the annoying problem that people know they're being studied and may modify their behaviour accordingly.