Now the elites plan to enslave everyone—and use the military to do it...
They already have...it is called ECONOMIC SLAVERY.
And I think that is what Mattis is conveying here.
He's speaking in code. By telling us he is concerned about "racial justice," he's using a code word--or dog whistle--for communism.
He's telling us that he and the military leadership are supporting the Ruling Elites in their communist coup. Though he is retired, he is still the face of the military to many. So without hearing from a general on active duty, we hear from an important symbol of the military.