The capitalization of Black is becoming increasingly accepted editorially due to its similarities to otherwise capitalized words like Christian, Jewish, Muslim, Marxist, Irish, etc. Essentially, a culturally distinct body of people.
"white" isn't capitalized because it doesn't bear as much similarities to those words, as "white" is not a cultural identity.
"white" isn't capitalized because it doesn't bear as much similarities to those words, as "white" is not a cultural identity.