That’s not true at all.
Slaves were certainly viewed as inferior to whites, but they were still considered legal persons. Despite what you said earlier, they were not legally viewed as simply chattel.
For example, while it rarely happened, owners who murdered their slaves could in fact be prosecuted for this.
Similarly, if a horse kicked to death his owner, the horse would simply be killed on the spot. Slaves accused of this were given trials, and on rare occasions even acquitted.
A better comparison would be to say they were legally considered to be similar to children.
I’d recommend anyone interested in this subject read Eugene Genovese’s Roll, Jordan, Roll, though I should warn people that it’s very jargon-heavy.
One of the points he makes is that one of the ironic consequences of Reconstruction is that in many ways Southern blacks of the late-19th and early 20th Century had less rights than their slave ancestors of 60 years prior.
Slaves in 1840s accused of rape, murder, or something similar were given trials and while usually convicted did sometimes get off whereas their grandchildren couldn’t even look forward to a trial but would simply be strung up from the nearest tree.
As he explained. Raw, anti-black hatred, as opposed to simple belief in child-like inferiority, really only came about following reconstruction. Lynchings for example, were exceptionally rare prior to this.
The reason for this was that during Reconstruction, blacks wound up puncturing one of white southerners more cherished fairy tales, that the blacks liked being slaves, loved their masters, and saw themselves as child-like inferiors.