That one sentence is not the message, the message is

  An extreme totalitarian surveillance state will 
  eventually converge to punishing acts like extra 
  marital sex or keeping a diary with personalized 
  torture until victims are broken beyond any thought 
  of hostility towards their authority figures. 

Which is a damn good thing for children to think about. People really are that bad, so hold your freedoms close.

What is the message then?

It's right there in The Party's second-favorite slogan:

    Who controls the past controls the future.  Who controls the present controls the past.

The task of finding similarities to current events in the world (and the U.S. in particular, this past year) is left as an exercise for the reader.