Maybe it is just difficult to comprehend things that are outside of one’s own narrow context. The black woman is not suggesting anything about slavery or black people belonging or being owned by others. What she is saying is that it is easy for any community to point at another and say that the community or it’s children have failed, it is another thing to say if all of those children fails then it will in some way eventually affect all of us.
She is simply saying that we should give a damn about other children because we all belong to one large community.