Ventriloquism 2

Imagine a horror film about an insane ventriloquist who believes that
his possessed dummy is talking. What he believes the dummy to be
saying is not what the dummy is saying. The dummy can appeal to the
audience, but the ventriloquist will not understand the audience's
reactions. Especially when the dummy tells the audience that the
ventriloquist thinks it wants him to murder his wife.

How can the ventriloquist silence the dummy? Even if he destroys it
or exorcises it he will only silence its real voice. He will still
hear what he thinks it is saying. And if his insanity is diagnosed
and treated after this, he will still be unaware of what he has
actually done.