This is a common, but easily corrected historical misunderstanding.
It was an economic rationale, not a statement of their human condition.
I don't think it's a misunderstanding at all.
Their "human condition" was that they were chattel property, little more than animals in the eyes of most early Americans (and arguably most or many Americans in general up until about the 1970s).
That an "economic rationale" would be the primary determinant of how this country, politically, viewed several million people speaks more to the uncivilized nature of 18th century Americans than any other argument I'd care to make.
And mind you, I'm not making some bleeding heart, anachronistic argument here for how I (may or may not) think blacks
should have been viewed back then.
I understand that the views those people had and the policy they made consequent to those views was a product of their times. They couldn't have taken a much more "enlightened" view of blacks.
My point, simply, is that as America continues to civilize and evolve culturally and socially we should expect that our laws relative to equality will civilize and evolve as well.
When the Founding Fathers were writing the Constitution it would never have occurred to them to insist that all people be treated equally or that it might some day be socially unacceptable to have some Sneeches with stars on their bellies and others without.
So, to me, saying "Well, the Constitution says nothing about requiring businesses to treat any human being who walks through the door equally" doesn't hold a great deal of water.
Of course the Constitution doesn't say that.
In fact it tacks to the polar opposite direction and says "some people are only worth 3/5ths of a person" (the ultimate reason it says that being largely irrelevant).
Fortunately we have a system of government that allows us to change our laws as our views about people, and how people should be treated, develop.