Nothing to hide

No uncorrupted man may fear this court, Mr. Hale! None! The nothing to hide argument is an argument often made by people who support government surveillance, especially when the loss of privacy involved is someone else's and not their own.

"Nothing to hide" is arguably the identical twin of the equally fallacious appeal to motive, both of which are further related to the argumentum ad hominem.

While the argument itself remains logically incoherent, attempts may still be made to render it practically or morally irrelevant — assuming your literal worldview is that people possess no inherent rights to privacy. The persistence and utilization of this flawed argument stems from many different variants on that political conviction, not from any basis in logic.

Form
It usually is this unsubtle.

Why the argument is ridiculous
Having something to hide, as it turns out, is not the only possible reason to object to mass surveillance, though it seems that proponents of this argument simply aren't aware of any moral/political/social principles that clash with mass surveillance. For one, the view of minarchism condemns "excessive" government (of which mass surveillance would be a flagrant example) as inherently bad.

Additionally, supporters of a assert that any invasion that isn't necessary for public safety, health, etc. is a violation of principle. According to them, privacy is useful and valuable and thus worth defending, which the "nothing to hide" argument completely ignores.

Further, the argument implies that withholding something indicates sinister intent. This is blatantly false. Why do people hide their genitals? Why do people hide stuff in safes? Why don't people disclose the contents of their diaries? Why do some people want to keep their phone numbers or the location of their residence a secret? Are they planning to commit terrorist acts with these things? This is called the "closing the bathroom door" argument.

The argument further presupposes that the surveillance agency would act in good faith, which is far from a certainty. In a similar vein, it assumes that the law is always completely moral; as an extreme example, if a law was passed demanding that all Jewish people were to be rounded up in camps, then hiding Jewish people from the government would be the moral thing to do.

And in the case of NSA surveillance, which keeps tabs on citizens' internet usage and phone calls with programs such as PRISM, innocuous activity is easily misconstrued to be of malevolent intent. Take your average RationalWiki user, a charming fellow doing research on 9/11 to counter claims of conspiracists. He Googles "9/11 bombs" or something similar. The NSA takes notice and concludes "this is a textbook case of suspicious activity." And before long, our editor is on a no-fly list or the modern-day equivalent of Nixon's "enemies list."