I have already created a plugin ( q2a-delete-hidden-posts ) for this Kai .
I am doing through testing on it . Because it is neccery as we are playing with lots of posts .
Once I release you can delete all hidden posts at one shot from your entire website . It has a powerfull ability to delete all the hidden posts (questions or answers or commments ) with or without any dependent posts . The Dependent posts also will be deleetd along with the parent posts . All points and counts will be updated as usual .
Just you have to go to admin panel and click Delete All Hidden posts Button . And you are done . Cool right ??
In next 2-3 days I will be releasing the plugin . :)