If you travel to Africa, there are places you can visit where black slaves were kept before being sold. What you learn if you tour these places - often it was indeed black and Arab slavers selling black slaves to Europeans.

The Arabs bought both black and white slaves, however. It was just the Europeans who only bought black ones. In the European colonies, for the first time, slavery became associated with skin color.

Historically slavery has been going on for thousands of years and has involved all races. The Chinese, the Indians, the Persians, the South Americans... everyone had slaves. The Greeks kept white slaves as did the Romans. So did Nordic people. And the life of these slaves was typically pretty horrible.

African kings did buy and sell other blacks as slaves before Europeans started to do it, and the word slave comes from "slav" - during the Ottomon Empire, white slave women were a valuable commodity for harems and white (and black) eunuchs were used. In Africa, Muslims castrated lots of black boys for use in the harems and only 1 out of 7 survived this brutal practice.

Of course the Europeans were taking boatloads of blacks as slaves, but they weren't going into the interior of Africa to source them - black Africans and paler skinned Arabs were the ones bringing enslaved people from their villages to the coast.

The experience of African slaves in America was unique and obviously evil, but to deny that this happened worldwide and to other races is just to deny history, and to deny that Africans (both black Africans and lighter-skinned Arabs) bought and sold slaves is also to deny actually documented history.