Don't know about the dim-witted white guy thing, but certainly some of the owner's families would have partaken in such behaviour, given that it would have been lust, yes, but mostly power play.
But anyway, I would believe very few American blacks whose bloodlines would still be pure as it was from Africa. In Australia there are not too many full blooded Aboriginals anymore and in New Zealand I think you could only could the number of full blooded Maoris on two hands or less, I'm led to believe.
One guy claims there are actually none left:
http://www.stuff.co.nz/dominion-post/comment/4003888/The-racial-purity-train-left-200-years-ago
To me it seems that we are headed for a single race on Earth with our global movements and liaisons.
What would we have to be racist about then?
"The historian E. Franklin Frazier, in his book The Negro Family, stated that "there were masters who, without any regard for the preferences of their slaves, mated their human chattel as they did their stock."
Ex-slave Maggie Stenhouse remarked, "Durin' slavery there were stockmen. They was weighed and tested. A man would rent the stockman and put him in a room with some young women he wanted to raise children from."[9]
And I've read where black negro breeder bulls were sometimes kept in pens and sent out to perform stud service to breeding females at the other breeder plantations.
"The purpose of slave breeding was to produce new (super) slaves without incurring the cost of purchase, to fill labor shortages caused by the termination of the Atlantic slave trade, and to attempt to improve the health and productivity of slaves. Slave breeding was condoned in the South because slaves were considered to be subhuman chattel, and were not entitled to the same rights accorded to free persons."
An advertisement in Charleston, South Carolina, in 1796, offering fifty prime Negroes for sale contained theses sentences: *** "they are
not Negroes selected out of a larger gang for the purpose of a sale, but are prime, their present Owner, with great trouble and expense, selected them out of many for several years past. They were purchased for stock and breeding Negroes, and to any Planter who particularly wanted them for that purpose, they are a very choice and desirable gang." At all times "breeding slaves", "child bearing women", "breeding period", "too old to breed", etc. were familiar terms.
Don't miss this though:
https://civilwartalk.com/threads/slave-breeding-fact-or-fiction.8767/
"However, some historians disagreed and argued that the practice of breeding humans as one would breed animals (to produce a desired offspring) did exist and the practice had the most detrimental effect upon the slave population. For example, Paul Escott found that breeding was often used as a mechanism to control not only the slave population, but also as a way of creating a new breed of slave".
Furthermore, Lerone Bennett acknowledged that many slave apologists deny the existence of breeding, but they ignore the evidence from the slave owners themselves. Bennett refers to the numerous anti-bellum advertisements that, for example, listed black females for sale as stock and breeding Negroes.
In Texas former slaves recalled the numerous examples of breedings and forced marriages during slavery. Former slave Josephine Howard remembered that her master put her parents together which produced six children. Likewise, former slave Silvia King indicated that she was abducted from Africa, processed through New Orleans and found herself the property of a man she called Marse Jones. In regards to forced marriages, King said, After while, Marse Jones say to me, Silvia, am you married? I tells him I got a man and three chilluns back in the old country, but he dont understand my talk and I has a man give to me. I dont bother with dat ******s name much, he jes Bob to me.
Former slave Sam Jones Washington also commented that his mother and father were placed into a forced union much like the parents of Josephine Howard. In fact, Washington said he did not even know who his father was. I dont know my pappy. Him am what dey calls de travelin ******. Dey have him come for service and when dey gits what dey wants, he go back to his massa. De women on Massa Young place not married.
Lastly, former slave Sarah Ford commented that her mother told her that some slaveholders would not allow some slaves to marry because it might reduce their productivity. She said, She (her mother) say de white folks dont let de slaves what works in de field marry none, dey jus puts a man and breedin woman together like mules. Iffeb the women dont like the man it dont make no difference, she better go or dey gives her a hidin.
While there is no historical consensus regarding slave breedings and forced marriages, evidence exists suggesting the slaveholder played an unwelcome role in the sexual behaviors of slaves. The depression era oral records of former slaves definitely indicate that female slaves were often forced into sexual relationships not of their choosing.
Sources:
Boles, John, 1984. Black Southerners, 1619-1869, Lexington: University Press of Kentucky.
Escott, Paul.1979. Slavery Remembered. Chapel Hill, NC: the University of North Carolina Press.
Fogel, Robert William. 1992. Without Consent or Contract, New York and London: W.W. Norton and Company.
https://sittingbull1845.blogspot.com/2014/10/black-social-history-slave-breeding-in.html
I guess that's enough on that, kind of an ugly subject to say the least!