If a corporation is going to transplant workers to a plantation in an unsafe place, then the corporation has responsibility for keeping the workers safe.

A big element of their case that's oddly not mentioned in this Guardian article is that the violence was foreseeable and nothing was done to stop it. The tensions did not bubble up overnight, and this was not the first instance of violence in an otherwise peaceful place. There were many signs that something like this could happen, and Unilever declined to spend resources on keeping the workers safe. As a result many of the workers were raped and murdered. Now the survivors are seeking justice, and they deserve it.

Unilever are the corporation who was ultimately profiting from the employees' work, so the survivors have a right to seek justice from them directly.