> “There is absolutely no physical way whatsoever for a fullnode to prove to an SPV node that it is telling the truth. All it can do is say “I’m saying something different than that other node.”
Read what I said: As you say, a user of an SPV wallet can’t currently get a fraud proof from their software. They get their fraud proof from ANOTHER HUMAN BEING.
This is the same way you get to find out when their software (bitcoin or otherwise) is buggy and they need to upgrade it to keep it secure.
Now, there may be situations where this process is too slow for you, and you need an automated process to know which payments you can trust sooner. But it’s absolutely sufficient for the things you say you’re worrying about here, like:
> This leaves all users not validating open to whatever rule changes to the system those validating decide. This turns Bitcoin into a tyranny of the minority over the majority.