I don't know how true all that is on the link, but more probable than not.
I think if all of us who's ancestors came to America in the beginning could trace back far enough, we'd find that we all had some black ancestry. Maybe none that effected us directly, but back during the slave days when it wasn't uncommon for the owners to have children with the slaves. The slaves always carried the sir names of their owners.
I know that back pre-Civil War, that one of my relatives (can't remember the relationship) fathered a child with a slave. The child was brought into the home and treated as their other children. Wonder how uncommon that was???
And, I have some first cousins who have been in interracial relationships or marriages and have children. Doesn't bother me in the least. There was some hullabaloo with some of the older members of the family years ago over this, but now we think nothing about it.