So the answer to the question, "Do black people practice polyamory?" is, "It depends." For example, it depends on religion and familial culture.
And the answer to the question, "Why don't more black people attend our poly functions?" is, "They're not poly functions, they're *white*
poly functions." A black person could attend a potluck here in Albuquerque, and all they'd be thinking the whole time is, "I don't belong here. I don't fit in." Skin color sure seems to be hard to get past.
I note, too, that there is quite a bit of variation between how inclined different black communities are to "make friends with the white guys." And that reparations tend to be rather futile, regardless of the inclination of a particular black community.
It's not easy for people to get past the ill will and hostility, between individuals and between cultures all over the world. The white man has made of himself a conquering race, and as such has done considerable damage that can't be undone. Not in this lifetime at least.