The most impactful racism, that is also the hardest to fix, is systemic racism. I think the idea behind buying from black owned businesses is the individuals attempt to offset the systemic racism that they, individually, can do very little about.
Celibacy is a lifestyle choice. Wanting sex and not having it, is not what I would call “involuntarily adopting a lifestyle choice”. Incel is rather, like you said, the feeling of being “unfuckable”. The problem, as I see it, is that the majority of men in this position are voluntarily “unfuckable”. They are actively being unlikeable by doing things like treating women like they they should be required to like them, which in turn, makes them “unfuckable”.
This sounds like something an incel would say.
Intentionally buying from black owned businesses does not perpetuate a racist white man that is in a position of power that allows him to deny black people economic power.