As much as I sympathise with you and anyone else who has fallen victim to what happened last night I think that closing the community overnight is an over-reaction.
By the way, you have given a good argument for keeping GD as a forum, and although it isn't somewhere I normally visit I agree with everything you say. I would also add that although during the night the community is fairly quiet it nonetheless serves a purpose for those who might need help, to chat, or just while away the hours when they are unable to sleep. So for those reasons I can't support your idea.
Last year I also started a thread which tried (and failed) to address the same problem as we are discussing now. However, we are now using a different platform and this time there may be a solution which perhaps @alex_w and @roxy_r could comment on as to whether it would be a) feasible and b) something they would be willing to implement.
My suggestion is that when the last staffer signs off at night he or she activates a "soft delete" function for all reported posts. This would make them disappear from public view but keep them available to educators to see and deal with the following day. When the first staffer signs in soft delete could be deactivated again.