Responsible for it's members - yes, to the extent reasonable by law.
Responsible for non-members - no. They are not members for a reason. While they may reflect poorly on a good, well run, organization, it is not the responsiblity of said organization to police other organizations. That's why they are separate. It should be CLEARLY stated in any press expressing the situation clearly.
Organizations should not be able to write or imply that they enforce the law other than governing bodies that are expressly made to do so. Police exist for a reason, and citizens have the empowerment to uphold the law within reason. The organization should work closely with law enforcement, and make streamlined communication tools to ensure those who should not be aren't (yes, it's worded funny; but it works). If an organization places itself above the law, it is saying that it is the end all. There is the off chance that a "*** offender" is not someone who ever hurt a child or even committed any form of sexual abuse. Public indecency, willfully or not, near a school or gathering of children is grounds for being on the *** offenders list in America. Accidental, or not. There are similiar situations where a child was never truly in danger, but the registry holds no differentiation. Further, there are individuals who SHOULD be on registries that are overlooked or ignored because of one reason or another. In situations like this, it is the club's/individual ownership that holds the responsiblity to put a frame work in place that protects the children. Cameras, open viewing areas, open doors and the like. Athletes should not be left alone with adults alone, and there is never a reason for this. Some parents may overlook this, but as a coach I never will. Children, as good natured and good hearted as they are, can really interrupt a career, or create a void of trust, simply by implying something bad happened when it really didnt, and have no grounds. Once the thought is out there, and the question of "did it happen" exists, generally it's as good as done. Coaches need to protect themselves, clubs need to protect their parents and coaches, and in turn - organizations should create a strong guide for what is expected of its members in terms of conduct. Enforcement should be based on severity and instance, with good evidence supporting the claims.
In the United States, people are innocent until proven guilty in a court of law. Given the situation, no organization should post a picture, personal information (other than public information such as Name for reference), or any other individually identifiable items prior to conviction. Since we assume innocence, doing any banning or posting of any materials, could be considered slander and bias towards conviction of guilt prior to a court ruling. This is slander. This is against the law. This is also dangerous to the individual, as it brings public opinion to bare on the individual, and mob rule is never pretty. While it may never get to an extreme that it causes a danger, the thought that a trusted individual may have harmed or abused someone's child may provoke anger and irrational reactions. Publishing personal information, even as little as a picture, may promote action that otherwise would not have happened. The organization needs to protect itself from such events, as well as its members. Post trial, I believe the institution should simply post it's stance on banning, it's stance on how it handled the situation, and keep internal information for future use that the public has no need of seeing. Again, coming back to a streamlined effort of communication with law enforcement, public records of name changes and location changes, should be tracked if the individual was a member of the organization - something the public has no need of knowing, nor any use for, but could be useful in preventing the individual from harming others.
In the end of the day, if the organization feels and individual is a detriment to it's message, goals, or philosophy, it has the right to ban or revoke membership as it sees fit. Just like any other group, it is protecting itself from exposure and from affiliation. However, it should also consider the consequences of it's actions and how the public will view those actions.