That's the problem, while you say we shouldn't use the argument that "spies need 100 percent transparency", they
do pretty much use the opposite argument, that we can never know anything about what they're doing, often even their overseers, because it would "endanger national security".
Plus, even though the 4th amendment clearly states that you can't even seize stuff from a person, without probable cause. Yet, they keep saying that they can, and it's ok to do it as long as they don't search it. They intentionally omit the seizure part of the 4th amendment.
Look at it this way. Would it be ok for the police to come into your home, no proper warrant other than a "general warrant", like the writ of assistance for which Americans rebelled against UK, and take your stuff, as long as they promise to not look through it?
I think that would be completely unacceptable and immediately be declared unconstitutional. Yet, NSA keeps pretending it's completely fine to take your "digital" stuff as long as they don't look at it.