Huge amounts of "wealth" crossed the ocean during the Transatlantic Slave Trade during the time piracy was at its peak in the same area. Did pirates ever try to raid slave ships to steal this "wealth"? If so, where did they take them? Did pirates have plantations too? If not, why not? Wouldn't that have been a missed opportunity?
u/Elphinstone1842 touched upon this topic in this answer.
To summarize: Yes, pirates did raid slave ships and they didn't feel too bad about it. Captured slaves were simply treated as captured cargo.