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.
Most slave traders weren’t “Yankees” but British, Dutch, Spanish, Portuguese, or French,
http://www.slavenorth.com/rhodeisland.htm
“Rhode Island, of course, was among the most active Northern colonies in importing slaves. Between 1709 and 1807, Rhode Island merchants sponsored at least 934 slaving voyages to the coast of Africa and carried an estimated 106,544 slaves to the New World. From 1732-64, Rhode Islanders sent annually 18 ships, bearing 1,800 hogsheads of rum, to Africa to trade for slaves, earning £40,000 annually. Newport, the colony’s leading slave port, took an estimated 59,070 slaves to America before the Revolution. Bristol and Providence also prospered from it. In the years after the Revolution, Rhode Island merchants controlled between 60 and 90 percent of the American trade in African slaves.
As a Rhode Island historian writes, “All together, 204 different Rhode Island citizens owned a share or more in a slave voyage at one time or another. It is evident that the involvement of R.I. citizens in the slave trade was widespread and abundant. For Rhode Islanders, slavery had provided a major new profit sector and an engine for trade in the West Indies.” Slaves that were not auctioned off were put to work aboard merchant ships. By 1807, black seamen made up 21% of Newport crews.
The Browns, one of the great mercantile families of colonial America, were Rhode Island slave traders. At least six of them — James and his brother Obadiah, and James’s four sons, Nicholas, John, Joseph, and Moses — ran one of the biggest slave-trading businesses in New England, and for more than half a century the family reaped huge profits from the slave trade. “When James Brown sent the Mary to Africa in 1736, he launched Providence into the Negro traffic and laid the foundation for the Brown fortune. From this year until 1790, the Browns played a commanding role in the New England slave trade.” Their donations to Rhode Island College were so generous that the name was changed to Brown University.”
http://en.wikipedia.org/wiki/Newport,_Rhode_Island
“During the colonial period, Newport was the center of the slave trade in New England. Newport was active in the “triangle trade,” in which slave-produced sugar and molasses from the Caribbean were carried to Rhode Island and distilled into rum, which was then carried to West Africa and exchanged for captives. In 1764, Rhode Island had about 30 rum distilleries, 22 in Newport alone.
Many of the great fortunes made during this period were made in the slave trade. The Common Burial Ground on Farewell Street was where most of the slaves were buried. Sixty percent of slave trading voyages launched from North America – in some years more than 90% – issued from tiny Rhode Island, many from Newport. Almost half were trafficked illegally, breaking a 1787 state law prohibiting residents of the state from trading in slaves. Slave traders were also breaking federal statutes of 1794 and 1800 barring Americans from carrying slaves to ports outside the United States, and the 1807 Congressional act abolishing the transatlantic slave trade.
A few Rhode Island families made substantial fortunes in the trade. William and Samuel Vernon, Newport merchants who later played an important role in financing the creation of the United States Navy, sponsored thirty African slaving ventures. However, it was the D’Wolfs of Bristol, RI, and most notably James De Wolf, who were the largest slave trading family in all of North America, mounting more than eighty transatlantic voyages, most illegal. The Rhode Island slave trade was broadly based. Seven hundred Rhode Islanders owned or captained slave ships, including most substantial merchants, and many ordinary shopkeepers and tradesmen, who purchased shares in slaving voyages”