“I never said they were, only that slavery was well established in the original colonies and the fledgling states before the purchase.”
This is a classic non-sequitor.
I have news for you. The Louisiana Purchase was (shocker) new land. New land for the United States - which it did not previously hold.
So, since this was new land, we are presented with a few options.
One of those options is that immediately all of the American slavers were so eager to buy this land and bring their slaves to this clean pristine land because it never existed with the institution before and was never upheld by previous empires before.
Since that one cannot be true, it must be true that slavery was already there and it must be true that the U.S. inherited slavery on that land from the previous empire.
In this case. The French Empire.
All of the facts check out. The U.S. inherited slavery through the Louisiana Purchase on that particular set(s) of land which were purchased.
You do not have to complicate this.
“shows that it was NOT a “peculiar” institution at the time”
That is fair.