Jayne actually mentioned this during the Q&A stream when it they asked about larger private MP groups. It would appear griefers are now showing up to the official MSFS live events and being general ***hats and nuisances to the group.
These griefers are everywhere. You can find them at most major airports buzzing the towers, buzzing approaches as planes are trying to land, etc. Every now and then, I re-enable MP. It takes all of a few minutes for me to remember why I disabled it in the first place and turn it off again.