Ah yes, what happen in Vegas, stay in Vegas, unless you get caught cheating at the tables, then every gambling establishment in the world will know, of and about you. That is also why there is a gaming commission to make sure the opposite is true. I look at forums the same. If you get caught with your sticky finger doing a naughty in a forum, then you get banned and other forums may learn about your bad habits. If a forum gets caught with their sticky fingers doing a naughty, then forum members are free to spread the word to other forums and their members.
If a person is a rapist or a child molester, I am not going to remain silent, so I don't get labeled a snitch. Response is and must be in proportion to the offense. An old TV program quote :"If you can't do the time, don't do the crime." If a forum or members don't want their posted information spread, don't post to the public. if it is a Private Message, do not share with anybody, The key phrase word is Private.
My rule is: If I learn something about somebody in a private conversation, I will not discuss that information with anybody else. I am not smart enough or sensitive enough to know if or what another may or may not want others to know about. Now if I learn it in an open/ public post, then I am free to comment. JMHO