Fascinating, because I just looked it up on there in addition to the English heritage dictionary which I originally used. The specific use case of discriminate being used in a social prejudice sense was even closer to the bottom than in my original post. So your specific dictionary doesn’t even support your claim, it’s predominantly used to describe being able to identify differences in a set of items.

MW dictionary:

a : to mark or perceive the distinguishing or peculiar features of Depth perception may be defined as the ability to appreciate or discriminate the third dimension … —H. G. Armstrong b : DISTINGUISH, DIFFERENTIATE discriminate hundreds of colors 2 : to distinguish by discerning or exposing differences : to recognize or identify as separate and distinct discriminate right from wrong especially : to distinguish from another like object discriminate the individual voices in the choir intransitive verb

1 a : to make a distinction discriminate among historical sources discriminates between literary fiction and popular fiction b : to use good judgment 2 : to make a difference in treatment or favor on a basis other than individual merit discriminate in favor of your friends discriminate against a certain nationality