I don't think that's a loophole. On the contrary, if 230 were reinterpreted to mean that online content providers were legally required to have no editorial control over user provided content, that would be a pretty significant departure from current case law.

Section 230 is quite short and (to my mind) somewhat vague, which I think lends itself to different understandings. But I don't think it could be reasonably interpreted to mean that online publishers cannot moderate user content as they see fit.