You'd be okay with forcing this onto people who don't want this, and the majority who won't even know that this is happening?
If it detects something and alerts the relevant authorities, there will then be a proportional reduction of privacy while they investigate, but this is true of any criminal investigation.
Doing it this way strikes a reasonable balance. Other alternatives include doing nothing at all, or sending a copy of all private communications to a third party - neither of which are desirable.
Why trust the executive without judicial oversight? What if they use their powers illegally, or misuse the files they receive? What if they are hacked? You will never know what happens in the black box.