Some don't want their old posts archived for eternity, for privacy reasons.

Yahoo had a nice interface to allow everyone that was a member of any group to download everything for their personal and private use, and it worked fine. Random external parties republishing other people's old posts though is not OK at all and is a massive breech of privacy, and is a violation.

Because of the threat that one's opinions may be archived and forevermore propagated by random third parties, at this point in history one would have to be insane to express a genuine opinion publicly. Therefore these efforts have a chilling effect on free speech and are inimical to democracy.