The argument for violating privacy in communications is literally that it is being used as a mechanism for breaking the law.

I'd be interested in hearing a logically consistent argument for why bad guys hiding illegally gotten gains is a legitimate reason for opposing banking privacy, but bad guys using encrypted communication platforms for planning crimes isn't a legitimate reason to oppose communications privacy.

In both cares, the information would of course only be available to the government who will only ever use it for Legitimate Good(tm).