"That's a little disrespectful to those who actually lived in surveillance states."
No it's not, and I highly resent this argument. It inevitably ends up with, but it's not at stasi levels... yet... When in truth what we have now would have made the Stasi have wet dreams! So stop it with this variation of affective fallacy already. Even if it was, somehow, disrespectful, which I don't think it is, even it was, who cares? It doesn't and shouldn't change the conversation whatsover. We are having a discussion about the current state of our mass modern surveillance engine, not about any other time in history (though they might be relevant to learn from).
Also, at this stage, if we don't talk about the potential before it gets too bad, we won't be able to stop it. Binney and Drake both refer to the current state as the "turn-key totalitarian state", and Drake for example got his start spying on east Germany during the cold war! As a matter of fact, if anything, I would find it to be highly respectful, for we are trying to prevent a similar fate those before us have failed to prevent.
"Tor makes it possible to do this with relatively little risk to yourself."
Nope, when they own enough fiber backbone nodes owning the tor network becomes much less non-trivial. Also, targeting tor-browser 0days, along with, as we can see from the NSA and CIA leaks, direct comprimise of machine, make tor not nearly as useful as a tool of anonymity as you seem to think. (Still useful, don't hate me J Appelbaum...)
"how much of a threat do you need to pose before they'll act against you in particular?"
Easy, all you need is to be effective and credible. It's been seen time and time again, since COINTELPRO and on. If you are just ranting and raving, maybe doing a protest or two, no one gives a fuck (other than to enter your name into a database somewhere). The second your protest actually starts doing something, or your dissident political campaign affects change in some way, thats when you become a target.
"The governments of old would routinely act against large numbers of their population for far less."
What's your point? First of all, with the surveillance engine storage, there is nothing to prevent the sudden repeal of ex post facto and suddenly they start walking the cat backwards 5 years, enmasse, against any potential dissidents. Remember there are over 1.1 million Americans on the "Terror Watch List", with no transparency of how they got there or any recourse to get off.
You say you aren't arguing for complacency, only for perspective, but your rhetoric does not match your claim.