I really do feel that mnet has a duty of care to intervene
No, no, no! How can they?! And what a terrible responsibility for MN to have to bear - seriously. This is just an online chat forum at the end of the day. None of us here knows how to help the OP, no matter how much we might want to. And it's all to easy for someone to say the wrong thing.
It's absolutely right that MNHQ should delete these threads.