So if you're a host after host rotation came into your turn, and you vandalize the room by kicking everyone, is it bannable offense? Is it allowed? I am just asking, I never planned on trying it.
No. When a lobby creator passes host, they are entrusting the user with all privileges. If they do not want their lobby to be abused, they shouldn't give host to a random untrusted user. The original lobby creator can use !mp commands to clear the host or kick the offender.
It's a dick move, but it's not something that can be punished.