The article states "Our instinctive aversion to incest is informed by intuitive eugenics" and links to a scientific study which supposedly asserts the same claim, which it doesn't. The study uses "intuits" which isn't the same as holding eugenics as a belief system. The entire article reads as a classic case of propaganda intended to reinforce confirmation bias in favor of normalizing eugenics.

Label away enough and it's perfectly normal to be a eugenicist. Why not natural?

Edit: and in the linked study, I'm not seeing any evidence that this can be reproduced among polyamorous tribes where close familial ties are comparatively vague or not recognized. If it isn't reproduceable, it would suggest any aversion people intuit toward close kin is due to some kind of social contstruct, being not innate.