>>14110053
Humanity is the sentient species in control of the resources this planet has. If you wanted those resources for yourself you might decide to infiltrate humanity at the genetic level, gradually weakening and destroying them from within. Dooming the species while remaining in the shadows. A silent war on the gene pool. Spread the bad seed more quickly by encouraging cultural shift towards promiscuity.
Imagine if that had been happening and some clever people realized it was going on. They might decide the only defense against such an attack was to remove the compromised genetics from the gene pool to save the species from otherwise certain extinction. Like a trapped animal chewing off a limb.
Such a program might look like a sudden global pandemic justifying vaccination of the entire species, with the compromised members being removed as a result. Saving humanity. Difficult truths?