I've found that bullies can be pretty manipulative. They can trap you into responding and then looking, or perhaps even being the bad guy and people come to their defense. Like to live rent free in your mind.
Often the best option is to just let them rot in their own disease. All responses to them should be focused on that goal--to render them inert enough that you can just walk away and leave them to rot, preferably in a very conscious way. Anyone that stays can stay.