Those are not related issues - it's malware or not malware based on what it does or did (e.g. did it corrupt data on someone else's computer system because it was intended to do just that thing?) regardless of the reason for placing it there.
If you can't figure out a way to satisfy your desire for your devices to be resistant to surveillance tools with legal means, well, then you can't satisfy that desire.
Furthermore, not only the ends don't justify the means, the ends can be prohibited too - if you explicitly design something to destroy your own data knowing that this data would get used in a criminal investigation, that may be a crime on its own (tampering with evidence/obstruction of justice, location matters of course); you don't have to testify against yourself, but destroying evidence is a crime even if it's your property (e.g. throwing your gun into a river after a shooting so it wouldn't be found) and furthermore in that case the court may be allowed to assume that the destroyed evidence was unfavorable to you, that the data contained the damning things they expected to find there - so if you want to protect your devices from surveillance tools operated with a legal warrant, you might want to consult a lawyer to find out if that's a good idea in your jurisdiction, it may well be worse for you than doing nothing.
> If you can't figure out a way to satisfy your desire for your devices to be resistant to surveillance tools with legal means, well, then you can't satisfy that desire.
I fear this part of your argument is fallacious. A peaceful and hilarious response to an abuse is not illegal. An if it is, it should not be. This post just highlights how petty the means and methods used by "some companies" are. Moxie is rightfully mocking Cellebrite and its customers, and it's fantastic.
About the obstruction of justice... If governments around the world are having an appetite for abuses, we shall not fall for it. There are other ways to get to criminals. Tell state officers they can do their job without abusing the private sphere of citizens.
It's Cellebrite devices that should be made illegal, because "justice" should not depend on surveillance tools. Just days ago the same US IC shared a memo/report about the rise of authoritarianism and how western democracies are threatened by it. Let's stop this double standard.
It is software that many of us are perfectly content with possessing on our devices. Cellebrite may not want it on their devices, but it's not like we consent to Cellebrite copying over our data. Holding us or Signal responsible for this is akin to holding a dog or its owner responsible for a burglar getting mauled - it would be one matter if the dog mauled a guest, but you can hardly blame either with unauthorised entry. In this case, exploiting this can be considered a form of digital rights management.
As for tampering with evidence, your claims are certainly overbroad, otherwise one could consider Signal's vanishing messages and deliberate lack of logging to be tampering with evidence. In any case, an individual is hardly responsible for those actions; they presumably did not deliberately seek to destroy Cellebrite data since Signal may choose to do this entirely at random.
If you can't figure out a way to satisfy your desire for your devices to be resistant to surveillance tools with legal means, well, then you can't satisfy that desire.
Furthermore, not only the ends don't justify the means, the ends can be prohibited too - if you explicitly design something to destroy your own data knowing that this data would get used in a criminal investigation, that may be a crime on its own (tampering with evidence/obstruction of justice, location matters of course); you don't have to testify against yourself, but destroying evidence is a crime even if it's your property (e.g. throwing your gun into a river after a shooting so it wouldn't be found) and furthermore in that case the court may be allowed to assume that the destroyed evidence was unfavorable to you, that the data contained the damning things they expected to find there - so if you want to protect your devices from surveillance tools operated with a legal warrant, you might want to consult a lawyer to find out if that's a good idea in your jurisdiction, it may well be worse for you than doing nothing.