I agree that "the Man" is being a bit sophomoric in his position, but I get the sense that he is just parroting what he heard someplace.

There are plenty of social scientists who have attempted to prioritize motivations in an effort to understand both normal behavior and weird outliers (like Janet Mason).

However, while you may have been asked to memorize certain components of somebody's theory by a lazy teacher (instead of actually understand what they were getting at and the limitations of these theories), the reality is that human behavior is not that concrete.

It is easier to memorize than it is to understand.