Did anyone say that having children of slaves become slaves was universal? I have quoted someone who thought it was unique to American slavery.

I hope we agree that the concept of race was a consequence of slavery.

There were free blacks in Birmingham in 1810, so I'm not sure your assumption is true. Not saying it's wrong. But do you have evidence that all free blacks had to regularly submit proof that they were free?

Rape and mistreatment of children may be traits of all forms of slavery. By definition, slaves have no rights or fewer rights.