"As the Americans learned so painfully in Earth's final century, free flow of information is the only safeguard against tyranny...Beware of he who would deny you access to information, for in his heart he dreams himself your master. Commissioner Pravin Lal, 'U.N. Declaration of Rights' "
This had until recently been only tested for top-down information. Nowadays, everyone can be a broadcaster and we're seeing quite different results.
Doesn’t mean a locked down system is better though. With that they don’t have to bother.
What you need is a decentralized system resistant to propaganda techniques.
Rather what you need is a means for propaganda to be rapidly identified and refuted with counterarguments in a way that its would-be victims can see it.
If you have a centralized system with Sean Hannity getting on the television and saying things which are clear, simple and wrong, you still have the exact same problem. Decentralization can only improve it because then it's not only him and the more complicated truth is at least available instead of the simple lie being the only thing on offer.
And this is what I mean by "in a way its would-be victims can see it".
People don't have time to investigate every throw-away simple lie, but it gives you the opportunity to sample. You follow Bob and he says a bunch of stuff and every time there is a whole complicated discussion that you usually don't read because you don't have time. But once in a while you do.
If every time you do, it turns out Bob is right, you can be more confident that the stuff he says is usually right even when you don't have time to check. If every time you do, it turns out Bob is wrong, the opposite. It provides the opportunity to evaluate credibility.
But that only works if you have a system where anybody can reply to anything and actually be seen. If you have a system where a central gatekeeper can make criticism and counterarguments invisible, you lose.