Lowest Common Denominator

I may find myself labeled a troglodyte or even a bigot for daring to question the sociology 101 people, but...

Isn't the "more differences than similarities" concept universally applicable to any naturally occurring set of individual objects?

Example:

Two and eighty-six are so-called 'even' numbers, while three and ninety-nine are both named 'odd' by Western Judeo-Christian traditionalists. Yet two has far more in common with three than with eighty-six...

It still seems to me that the whole premise is just an obfuscation used by instructors to get statistics-crazed undergraduates from digging themselves into a hole.