This is why I don't work well in many workplaces. I can't be a doormat.
In labor industries, it can get people killed. In finance you can be held legally liable. In retail, it can drive people to suicide.
If you don't have a code of ethics that you're willing to enforce people will suffer. Even if it's taken out of your hands, you can choose to walk away. As the saying goes, "With a gun to your head, you can always choose to die"
Just make sure to make a display of it so there's no doubt you've washed your hands of it. Raise your voice, project it, be absolute. Be wary though, make sure you also know how to throw down. Challenging authority always comes with risk.