“Antiracism” is another name for “critical race theory” which inherits from the general Marxist body of philosophy, of which “critical blah theory” tends to be a common name. Like “people’s republic” — it’s a fashion thing.
In sociology and political philosophy, "Critical Theory" means the Western-Marxist philosophy of the Frankfurt School, developed in Germany in the 1930s and drawing on the ideas of Karl Marx and Sigmund Freud. Though a "critical theory" or a "critical social theory" may have similar elements of thought, capitalizing Critical Theory as if it were a proper noun stresses the intellectual lineage specific to the Frankfurt School.