I don't know how the law currently works, but it seems reasonable to me that it should be the responsibility of the government to determine what's legal and what's not. I think Amazon would not be acting improperly if they alerted law enforcement that they suspect illegal activity and then waited for the authorities to issue an official order to take down the content (presumably based on a court order). I get that the current ToS allows Amazon to terminate the relationship unilaterally, but I don't think Amazon has to do that morally. And if they have to do that legally, I think it's fair to ask that the law be changed to allow private organizations selling a platform to not have to determine the legality of the actions of their customers. The FBI, police, and courts can do that.