I think they are: the sociological definition of a minority is a member of a class which is socially disadvantaged (sociologists talk about women as minorities for this reason) and a sociological "-ism" (racism, sexism) is policy or decisions which disadvantage the socially disadvantaged.

Presuming that position, it's understandable that they further believe that not favoring the disadvantaged is continuing the status quo, which is a disadvantage to the already-disadvantaged, hence the sociological "-ism".