The reason MNHQ delete the posts from FB is not because of the posts themselves, but because of all the people who post subsequent defamatory comments in the posts that follow.
For example, if bot is named in a post, then someone calls them a con artist in a subsequent post even if they are then both the poster and MNHQ have to be sure they could prove that claim definitively in court, if called to do so, or else they will face a big libel payout.
However, if the bot is it named in the post, then there is no libel because you cannot identify the person being defamed.
In other areas of the site, there is lots of defamation that is let slide. However, FLP have apparently made it quite clear that they are willing to take civil action if they are libelled. If you're up against a litigious company then it's worth protecting yourselves, as much as you can.
FWIW I think MNHQ have been extremely brave to let these threads stand, given we have no idea of the level of pressure they're under from FLP. They possibly have a public interest defence, but that's relatively untested and shouldn't be relied on.