Nah, you have to ask why he thought it was important to trumpet this fact, and then basically to lie and state that all of them did it for the same reason as white slave owners...., economic gain. That's not true, and he leaves out the other important reasons that Gates mentions.
Also, we're talking about 13,000, out of 2,000,000 - 4,000,000 slaves, so it's a minuscule percentage. 0.3% - 0.6% of the total slave population, yet he's embraced it and trumpeting it as if it means that slavery is A-okay, or not that bad because a very few blacks were able to purchase family members, purchase freedom, and for a very few, use them for profit.
@cooncreek, doesn't get credit for trying to expand his view of the world, but let's see if he'll answer why he posted about such an infinitesimally small pattern.