I think they're really talking about scientific stereotypes.
It's this kind of thinking that starts to give rise to so-called scientific explanations of why certain races are "inferior". The average man concept lets you compare races and genders and all sorts in a way that can appear scientific - in method at least - whilst ignoring the fact that there are so many variables to account for in the human condition, that any result must be taken with a lot of skepticism.
But people in general, particularly around the time, were astounded by the leaps and bounds that science had been making. So anything "proven" in a scientific enough manner, must be true. No skepticism to be found.
It's this kind of thinking that starts to give rise to so-called scientific explanations of why certain races are "inferior". The average man concept lets you compare races and genders and all sorts in a way that can appear scientific - in method at least - whilst ignoring the fact that there are so many variables to account for in the human condition, that any result must be taken with a lot of skepticism.
But people in general, particularly around the time, were astounded by the leaps and bounds that science had been making. So anything "proven" in a scientific enough manner, must be true. No skepticism to be found.