Fundamental processes of hegemony... is a form of rule where the dominant group exercises the leadership over subordinate groups via the development of the conscientiousness, rather than an exertion overt strength.
If you look closely at language-focused discrimination, you will find that it is not language per se that is relevant; instead we need to understand the individual's beliefs about language and following from those beliefs, institutional practices.
This "total system" of hegemony requires that the leading group secures it's position via the willingness and consent of the minority group. This consent is secured through the manufacturing of mass consent, a mass belief, of the naturalness and correctness of this social order.
When speakers of devalue or stigmatized varieties of english consent to the standard language ideology, they become complicit in it's propagation against themselves their own interests and identities.
I imagine the African slaves hearing spoken English as the oppressor's language, yet I imagine them also realizing that this language would need to be possessed, taken claimed as a space of resistance.
Successful resistance may lie in the usefulness of the dominant language.
The paradox, then, of linguistic hegemony is that one must "buy into it", acquiesce on some level in order to resist it.