As a pot might demonstrate the rich black hue of the kettle?
Interracial marriage was not the issue. Slavers used to rape their female slaves in order to get them pregnant with mulatto children, which fetched a higher price.
It's a mistake to confuse what the article calls preference - i.e. behavioral barriers to mating - with human decision making. Behavioral isolation is hard wired into animals, whereas humans can choose with whom to mate.
Which is getting to my point. The article was sloppily worded. or the definition of "prefers" was incorrect.