It's all related to the issue of Sec. 230 reform. The Courts have ruled Sec. 230 was intended to encourage internal, self regulation. An opt-out policy is exactly that--self regulation. In the absence of self-regulation, there will be a Mothers Against Defamatory Dissemination (MADD) style lobbying movement to force rewriting the Law; and the Congress people who write the Law will grow tired of responding to allegations they are pedophiles & holocaust deniers.
So it's a simple question: the industry either self-regulates, or the government will self-regulate you on your behalf.