Yes, the question of current purpose is nearly irrelevant. It's the question of possible purpose that's concerning because once it's A) available & B) left to human subjectivity then privacy & 'innocent until proven guilty' is no longer guaranteed.
This is the first time I will be on this other side of this argument, but let me disagree. The technology behind it isn't inherently bad, it's the people running the system having access to it that scares us. Take Snowden for example; when he exposed what the NSA was doing with US citizens data (with the help of big companies), do you think he meant that the internet or security cameras are the threat? They sure as hell are a good vector, but you don't trash nor blame your pc for being the mean though which that is achieved. The problem is who we put in power and how we held them accountable for misusing it.
Right, but the moment you're relying on who is in charge then the process is already broken. You have to assume the process is usable no matter who is in charge. I know it's absolute, but it's the only way.
The process is broken if the people you rely on suck. It is inevitable that someone, in a form or another, will be representative of the group of people you are part of (may it be a dictator, an influential priest, or an elected representative); we have the luxury of living in (somewhat?) democratic countries. The way out of surveillance misuse is making (or forcing) our politicians pass laws that restrict what companies or agencies can do with our data, or how they can use them. I think spreading awareness about this topic is the most effective way to push these kind of rules in effect.
While individualistic "guerrilla privacy" might be effective for yourself, it's like a band-aid on a broken bone. If 99% of the people around you don't care about it, or simply are unaware (family, neighbours, friends), you will join the surveillance system no matter what: from a family member uploading your details to meta, to a stranger taking a picture with you in it and posting it, to your neighbors ring camera, to your friend's iPhone constantly scanning the surroundings to report nearby devices (your phone, for instance) to "improve location data".
If there is no laws that prevent evil actors from misusing this power, really little changes in the bigger picture by you using signal or protonmail (while you should do it, don't get me wrong).
EDIT: i know this will be controversial, but to me this is a good metaphor for it: the world is slowly getting hotter due to companies just caring about profits and politicians passing no laws to reverse the process, while instead actually taking bribes from those companies to not do anything about it (look, look, it's the same duo again) and your solution is... You dig an underground bunker to survive the next heatwave/hurricane.
I guess this is where I'd love to have this discussion in person over a drink of your choice because my point, albeit unclear, was that these systems that, on the face of it, "solve crime" shouldn't exist no matter how much 'good' they offer. They have no control &/or limitation to their powers except by the person who decides to use them. I don't see that as manageable. Ultimate power breeds ultimate corruption, if you will. It seems we're at an 'agree to disagree' point & I'm OK w/ that result. Have a good day/week/month & please continue your efforts to healthy debate!