It is not a new concept that defendants of freedom of speech often have to protect scoundrels too. The argument doesn't change, it always has the same pattern and principle. And yes, it is advisable to err on the side of freedom, there is enough literature here to expand on that point.

Additionally the agencies that would demand these information are prone to break the law itself. So this isn't even a discussion about doing something just or not. This is purely a discussion about how much power you want the executive to have. Or in case of Germany, the often misdirected and overworked judicative branch.

Criminals and fraudsters will abuse pretty much every technology they can get their hands on. As a consequence, every service operator needs to do their part to prevent fraud and abuse. If you offer a service anonymously and indiscriminately, your service will be overrun by crooks, and you'll end up serving criminals.

The fact that your service could be used to defend free speech does not absolve you from your duty of monitoring the use of your service. If you realise your service is used for exchanging illegal content and bomb threats, it's your duty to do something against that, or stop providing the service.

Except that line of communication puts your address on whatever it is sent by who-knows-who

A "perfect proxy" does that by design pretty much. Law enforcement can't know what was on that address until an inquiry

Freedoms and laws apart, that's the problem here

Yeah, I used to think in good-or-bad, right-or-wrong, black-or-white terms too... Then I grew out of my teens.

This is about bomb threats.