An e-mail:

Because that would be an admission by Hollywood that the blood/sex/language
is gratuitous. If it can so easily be removed from the product, it didn’t
need to be there in the first place.
There are already products similar to this. TV Guardian searches the closed
captioning for objectional words, muting the audio track and replacing
the objectional word with another word. It’s OK as it goes, but when
watching
the story of Jesus and seeing him tell Peter “Before the jerk crows, you
will betray me three times”, you realize that language is a tricky thing.