Had whites tried to roam the African environment during the Jamestown days, taking unwilling people from their habitats, they would've been slaughtered as quickly as they could supply more people to be killed.
Slaves were obtained at African markets, "bought" from (black) African brokers. There are still sellers of slaves all over Africa, the Caribbean, Arab countries and parts of Asia. Very few of these brokers, if any, are white. As a matter of fact, whites have done more to end the crime of slavery than all other races, combined times 10.