If the government hasn't done anything wrong, then they shouldn't have anything to hide from us :) More seriously, some amount of surveillance is probably necessary, but they need to be a lot more open and transparent about it. Secret laws and secret courts are not the stuff a free society is made of.
Governments have a legitimate need for secrecy in some situations. If FBI investigations of white collar crimes were posted on a public website, for example, there would be a dramatic rise in both flights and wire transfers to Belize. The blame here lies squarely with legislators that have drafted laws that are intentionally worded to give the public a false sense of privacy while enabling agencies like NSA to run am…
I think this argument is based on a strawman. The 'secrecy' most people assume and that the government wants is 'keeping secrets indefinitely at their sole discretion'. The 'secrecy' needed by your or any other scenario is merely a time-limited secret, ie. that all information must be released publicly once investigations are completed. The former is intrinsically harmful, the latter shouldn't harm anyone.