The fundamental argument isn't that the power (indiscriminate & pervasive one-way invasion of privacy) wielded by the NSA is actively being abused (which isn't to say it's never abused, but that's besides the point), rather, the argument is that, as a democratic and free people, we should be staunchly opposed to freely granting the right for such power to exist.
If one of our primary objectives as a liberal, democratic society is to avoid that kind of oppressive totalitarianism (as would be expected of a liberal democracy), then we have a duty to seek and employ the most effective strategy possible in avoiding that outcome.
Two things are required for the type of totalitarian surveillance described in 1984: the technological means and the will of the state to demand such evil acts be committed.
I'd argue that the best strategy to prevent an outcome that requires both means and will is to target the means. If the means exist, the state lacks only the will to utilize those means for evil ends (putting people in Room 101).
If the state lacks the means, then even once the will to do evil does inevitably come along, the state will be rightfully shackled and lack the requisite tools to enforce such tyranny.