I agree that criminals will use secure communications regardless of the law. I don't understand what you mean when you say it will increase crime though.

Regardless, I feel like there's a deeper motive from governments/law enforcement. It would allow them to claim that anyone using secure comms must have something to hide and is thus a criminal. Combine that with mass surveillance and anyone you see sending encrypted traffic can automatically be assumed to be a criminal. I'm not saying this is right, it's certainly not right. But I'm sure that's the argument that will be used by those trying to push it.

The only way to fix this is secure-by-default comms, such that all traffic looks the same and you cannot make any claims of criminality based on that alone.