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.
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
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.
Arguments like "we all need to abandon privacy to maybe, potentially stop some crime somewhere" are equally silly.
Everyone should avoid silly arguments.
It's not an assumption at all. The fact that people engaged in child pornohraphy have had decrypted communications used against them in court demonstrates this to be true.
Ephemeral conversation is not new and implicit in a right to privacy assuming it extends beyond your actual corpus.
The only way I understand your arguments to be a justification to break encryption is if you believe we should not have freedom to share privately.
It only demonstrates that for some people, it's true. What about cases where they were using secure channels and thus haven't been caught/charged?
Perhaps we should aim for not leaving any piece of space on Earth unsurveilled?
But the argument doesn't even make sense. It makes the horrible assumption that pedophiles will continue using a service they know to be insecure. 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.
And ALL of the above assumes that there are no criminal programmers and thus they have no ability to just write their own tools if there isn't something sitting on the shelf. We know with 100% certainty this is also a false assumption.