An conscientious objection is definitely a right you have as a professional, but it's a neutral action, you refuse to do something, and you let someone else do it. If you really are against it, you actively do something about it, like presenting a law or making a criminal complaint.

That said, they are both compatible, you can refuse to do something, and make efforts so that nobody does it.

But I think the the latter is the actual core security model of our society, and refusals aren't really effective to the point that I wouldn't worry much about it and just focus on compartimentalizing and executing on my duties. Isn't it theoretically possible that upper management divides duties so that engineers cannot accurately judge the ethical correctness of the task and the overall mission? As an individual you don't have the right tools to make such an evaluation. You can be pushed to investigate further, but the moment you do so, you cease your role as an engineer and put your citizen hat on.

I personally wouldn't object on most cases, my threshold would be very high, a database of people's sexuality is not even close to even being concerning to me, that's like a Wikipedia infobox property. But even if it were a feature that did concern me, like a citizen-ID to real time coordinates system, I wanna be at the helm of it, either way (if I get the privilege). If something is wrong, I'd be in a privileged position to do something about it internally, judicially or through congress, there's also whistleblowing if it comes to that, but that's not in me.