"....Is there any other way to understand killing and persecution for pleasure?"

For pleasure???
Whaling for pleasure????????
Going to sea for maybe a year or more, in a wooden ship, in the ice and snow or in the unpredictable tropics?
For a small percentage of the profits?
At great risk to life or limb?

As for slaving, don't forget to include "Alabama John Cherokee"
Kendall got it right on the button as usual,
"Sing whatever you want. If most people like it, do it again. If most people don't like it, drop it."