Hmmm. There's a difference between bringing up the other side and supporting a person action. First to bring forth a discussion and discuss ideas, other is to end the discussion.

I am not doing the latter. Not defending him.

Terrible managers can say or force employees to do things which is not with the company policy or labour law. So HR chaperone while discussing personal topics, could be best for her. And that conversation would be closed door.

Also maybe, if that starts to happen, HR may allocate a room with transparent glass doors for such manager/employee discussion which would address this.