You might do some googling on the myth of the class reductionist. By "critical race theorist", you must mean "neoliberal"--see the politics of Derrick Bell, Kimberle Crenshaw, etc.

King did not speak of capitalism as a tool of white supremacy. He spoke of white supremacy as a tool of capitalism.

Relevant:

“If a white man wants to lynch me, that's his problem. If he's got the power to lynch me, that's my problem. Racism is not a question of attitude; it's a question of power. Racism gets its power from capitalism. Thus, if you're anti-racist, whether you know it or not, you must be anti-capitalist. The power for racism, the power for sexism, comes from capitalism, not an attitude.”