I presume you have heard of McCarthyism? There are many, many examples of American abuses on American citizens, where innocent people lost their jobs, friends, families and even lives because of what they believed, or even what the
American Government thought they believed.
Imagine the McCarthyism mindset combined with today's surveillance culture and the disaster that would be.
Are you saying that at no time in American history has the FBI or NSA intercepted someone's emails, telephone calls or internet use and used that information to either capture them or force them into becoming a mole?
As for the OP comment about the grandkids and child porn - that was a front page story a few days ago on HN.
Catch 22. Worth remembering that this is a secret program, governed by "secret law", run by secret police, with strong penalties (including international manhunts) for those who expose abuses. You want us to rattle off incidents? Then start by giving whistleblowers immunity to actually report abuses.
The "secret law" part is the one that really floors me. The FISA court orders are themselves secret. Ignorance of the law is no excuse. But knowledge of secret law is itself a crime.
For context: you're referring to Steve Clemons reporting on overhearing a bunch of people affiliated in some way with foreign intelligence services babbling at an airport about how Snowden should captured or killed.
When I hear someone who works for the USG talk about how we should turn some supposed adversary of the US into glass with a barrage of nuclear missiles, I do not immediately fear for the future of the planet.
I hope the people Clemens overheard are identified.