"That example of obscene overreach and abuse of a government agency does not count because it is nothing more than an example of obscene overreach and abuse of a government agency."
I think the argument is that you need more justification to claim that a government agency is engaging in blackmail and extortion than "a once in a century character in a different government agency 50 years ago at the height of a national paranoia not seen since that time sent someone a nasty letter."
I agree with you, but I was responding to the claim:
"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."
Fears and cautions should not be tied to organizations themselves, but rather to actions. The NSA is not the FBI, yet memories of Hoover should give pause to anyone considering the NSA.
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?
I don't think anybody disagrees with the broad point you're making; this subthread is talking about how likely it is that the FBI is blackmailing people and trying (clumsily) to convince people to kill themselves based on the actions of Hoover's FBI.