As did the ruling class in the South. 

Mississippi Declaration of Causes:

"Our position is thoroughly identified with the institution of slavery-- the greatest material interest of the world. Its labor supplies the product which constitutes by far the largest and most important portions of commerce of the earth."

Georgia:

"... their declared principles and policy they have outlawed $3,000,000,000 of our property" Property - as in human slaves.

The State's right was the right to own people for economic reasons. Bringing up Great Britain is just more whataboutism.