If you are not putting in best effort to moderate harmful (not merely undesirable but someone is being harmed) content then by all means chill away. Key word is

If you are not putting in best effort to moderate harmful (not merely undesirable but someone is being harmed) content then by all means chill away. Key word is best effort with the resources you have. So a one guy operated forum has to restrict user registration to a volume that person can manage. Moderation is the way you avoid liability. Spam or dmca would be out of scope for example and a flag button is sufficient for reporting harmful content. The driver in a robbery-murder gets charged equally with murder because he was part of a criminal act knowingly. Merely facilitating content delivery is being the driver,so the moment you know a crime is being committed or someone harmed you have a choice to stop participating and report the offense or keep doing what you are doing and become a co-conspirator.