We don't need concrete proof of current wrong-doing in order to take lessons from history. That is the value of history.
"b/c it has nothing to do with an investigation...now blackmail and extortion???"
I read that as something stronger than "we need to take lessons from history." I think the statement goes further than that to claim that the NSA's purported justifications are entirely pretense and the real motivation is blackmail and extortion. That I think requires stronger proof than "someone sometime did something."
Have you read Caro's _Power Broker_? If not, you should!
Tying fear and caution to organizations prevents you from learning much of anything from history as the offending organizations are almost all abolished, abandoned, or reorganized. Should experimentalists working in medicine and the humanities not learn from the Tuskegee Experiment because Public Health Service is a different organization today and the Tuskegee Institute no longer exists in a meaningful way?