the detail does not describe a toxic boss. Bad, yes; toxic, hardly. Even the best boss needs positive reinforcement.
Toxic bosses poison the work environment in the same way chemicals poison the ground and water. The only way to 'clean up the mess' is to remove the poisons; covering it with dirt (i.e. being nice) only hides the problem; the poison remains. And you can be very confident the toxic boss was "dumped on you" with full knowledge of the dumper, who will protect his poison pill until it becomes a liability to him (or her) self.
My suggestion? Leave.
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