It's not their job to fix someone else's bad idea.
You don't want that. So we're at a bit of an impasse.
Distributed systems these days mostly argue that you do your trusting up front, outside of the protocol itself. You then validate that the actors share the secrets you all agreed upon, and then optimize the agreement process. Only the most robust systems actually consider "active" dissent; most distributed systems engineers consider this a special case that is most often focused on the idea of "incorrectness" as opposed to "maliciousness."
You can see elements of these assumptions in more modern data structures used for eventual consistency, like CRDTs. CRDTs are amazing and fast and often abstract-able to a trivial programming model. Anyone can use them, but they have to be monotonic, so we can't ever forget bad input, just try and cancel it out.
That's not really what I meant by "bad". I meant bad as in intent, not structural and immediately verifiable message integrity.
If all entities in the coalescing set can independently verify that a message does not meet its signature requirements, it will be rejected and idempotence is maintained.
If ONE member is somehow deceived about key validity it'll propagate the message into every other member's state, eventually.
Blockchains are a social construct and what ultimately protects them are the participants. Exactly like actual currencies they are subject to market forces; people either believe in and want the currency or they don't. It's this confidence that gives the currency strength.
More simply:
"On medium to long time scales, humans are quite good at consensus. Even if an adversary had access to unlimited hashing power, and came out with a 51% attack of any major blockchain that reverted even the last month of history, convincing the community that this chain is legitimate is much harder than just outrunning the main chain’s hashpower. They would need to subvert block explorers, every trusted member in the community, the New York Times, archive.org, and many other sources on the internet; all in all, convincing the world that the new attack chain is the one that came first in the information technology-dense 21st century is about as hard as convincing the world that the US moon landings never happened. These social considerations are what ultimately protect any blockchain in the long term, regardless of whether or not the blockchain’s community admits it (note that Bitcoin Core does admit this primacy of the social layer)." [1]
[1] https://medium.com/@VitalikButerin/a-proof-of-stake-design-p...
The subtlety here is making the distinction between confidence and resistance to attack. They're not the same thing at all. And what's interesting here is that, going off the model of real currencies, one could assume market forces will prevail here. Developed nations let their currencies float precisely because on the whole they're confident that the market will ultimately punish any malicious attacker who attempts to destroy the currency by selling large amounts of it.
