Who is hosting the blockchain? Who is the trusted authority over the maintenance of the protocol that implements the blockchain, that all miners must use if they want to participate in the system? Who is it you're trusting not to organize a malicious 51% attack against the system, when it has already happened several times to quite a few blockchains? It is a blatant falsehood that blockchains don't have any trusted authorities. They actually require trusted authorities to function. You're not trusting "emotionless code" as the code is well known to have these flaws even by the admission of its own designers; what you're actually trusting is some game theory laid out by programmers you trust, that says the miners won't do bad things because they're getting paid. But in several cases we've seen that they actually will do bad things! And that's not even considering all the other bad things like fraud and ransomware that happens on blockchains that the operators seemingly just throw their hands up and don't do anything about. They don't even consider that to be their problem.
I hate, hate, hate that this line is used so often in discussion of cryptocurrency. It makes no sense at all. In order to have any kind of real discussion around this, the crypto community needs to move past these thought-terminating cliches.