Not defending slavery but the worst part of slavery, the most dangerous, was the transit over on the cruel Yankee vessels run by tyrannical and sick scum of the earth Captains. It was so unnecessary. Not all vessels were Yankee registered and operated, but most were.
Crocodile tears on your part. Plenty of slave owners were tyrannical and sick scum themselves who didn't care where their labor came from or under what conditions it was transported.
Most slave traders weren't "Yankees" but British, Dutch, Spanish, Portuguese, or French, and most of the slaves who came to the 13 colonies or the United States came on their ships.
That doesn't excuse Northern participation in the slave trade. It doesn't exclude Southern demand for slaves either. Slave ships registered in Charleston brought a lot of slaves to these shores. I doubt all of them were owned by "Yankees," and note that as enforcement dried up the slave trade, Southern slave-owners, who'd been content to let others do their dirty work, equipped ships of their own to run blockades.
It wasn't necessarily morality that made slave-owners avoid that dirty work: they tended to avoid labor of any sort, so it's not surprising that they let others do their work for them. But there's something disingenuous about your accusations. Everybody came from somewhere. Northerners and Englishmen who settled in Charleston or Savannah and outfitted ships became a part of Southern society.