That's literally a provably false assumption. 
  The second they realize it's insecure (which 
  will take exactly one raid), they'll switch 
  to something else.

It is trivial to prove that the second a criminal realizes a given communication mechanism is insecure they do not stop using it if it is convenient.

Has every criminal in the world stopped using the phone after the first phone was ever tapped?

  And ALL of the above assumes that there
  are no criminal programmers and thus they
  have no ability to just write their own tools

But we know there are more than 0 non-programmer criminals who will not be writing their own tools.

You need better arguments than "if we can't stop all crime with an action it has no value" because it is a silly argument.