We've tried a few times to debunk
the ridiculous logic of "if you've got nothing to hide..." argument in favor of surveillance, but leave it the awesome Saturday Morning Breakfast Cereal to do a much better job in the form of a simple webcomic
In case you can't view the comic, the key line:
Everyone has something to hide and usually no one cares. By surveilling everyone, you catch the benign breaches of law and taboo. If the public are all guilty, the executive part of the government can selectively enforce laws, essentially giving them both judicial and legislative power, which defeats the whole point of separation of powers.