>>279991672
>Roger shows up to stop Rocks from hurting the CD's and freeing the slaves
Roger doesn't need to justify shit, he's a pirate and was only there in the first place to fight Rocks.
>Garp shows up, ignores the slaves being slaughtered just to fight Roger (and Rocks)
Harder to justify, but Rocks was likely extremely dangerous with extremely dangerous ambitions of wanting to become King of the World. We need more info though.