Does this jump into the "something/nothing to hide" argument?
The idea that there's an intentional backdoor through security for some institution that may or may not be acting in your best interest is enough for me to not want to use it.
Just about everyone has something to hide, but what they're hiding and the reasons they're hiding it may only be used as leverage against them and have nothing that's a threat to anyone else. My encrypted data has some old tax returns and past medical records--nothing too exciting or compromising, but neither are things I want random people having access to should my copy of the data be compromised.
There are plenty of valid reasons not to want a government agency to be able to pry into every aspect of it's citizens lives. I'd say most people hiding things do it for a lot of social/cultural purposes that aren't too significant at least not in terms of national security.
Take most peoples' browser history--few people want others crawling through searches that might make them feel stupid or insecure for whatever reason. Perhaps they looked at someone's public profile they're interested in dating and don't want to be labeled a 'creep' or perhaps they've been making great use of the free PornHub Premium access lately. People have rights to secure/hide those things and they're no real threat to national security.
That’s not the question. The question is, why would opening source to the NSA cause you to lose trust in the quality of work.
You seem to have answered the question, “Why is privacy good?” Your answer, at least to me, seems valid, but if you are answering other questions, I would ask, “Can you imagine situations in which individual liberties are trumped by physical safety of a large number of folks?” How have you reacted to CoVID-19 restrictions? Are those two things really so different?
