How does slavery victimize both the slave and the slaver?

A victim is one who suffers loss, injury or death due to something or someone.

A slaver or more accurately a slave trader and/or slave owner was not a victim. They were the perpetrators of the losses, injuries, suffering and death of black slaves due to acts of racial discrimination, abuse, rape, violence and murder to maintain control of human beings as their property. Black slaves were victims of exploitation for free labor and profit to support the economic development and expansion of the United States. They were not in a position to victimize 'slavers.'