It's not "every group of people" -- it's organizations that invite the participation of the public, or at least of others they don't know well, as long as they adhere to the mores of the community.

More importantly, I take the parent's point to be, not that such an organization "owes" anything to anyone, but simply that anyone formalizing a Code of Conduct and a committee to enforce it would do well to understand why the protections of due process exist. If their intention is truly to create a safe space for interaction, setting up a process that can be easily abused is not going to help with that.