It is not a secret for those who want to realize that the control of the world is centralized in powerful and influential families that can control the economy of even a continent, and with capitalism, controlling the economy you can control any sector.
What if, with the globalization of cryptocurrencies, they obtained the key they need to solidify their centralized control over the world? And if in reality someone knew how to hack the blockchain?
And that we were all wrong, thinking that we are decentralizing the economy, when in reality we are contributing to the creation of what could be the perdition of our liberty.
(I used google translate since I do not fully master English )
I'll contend: no to your question of whether decentralization is a secret plot to influence society into abandoning rights and freedoms. And: no crypto currencies will not solidify centralized control over the world.
A New World Order consisting of a one world government being "ideal". The concept of one world currencies being "superior". The idea of state based rights needing to be abolished in order to bring about innovation and progress. All of the major plots aimed at depriving people of rights and freedom are heavily centralized in origin.
Decentralization as presented by crypto merely illustrates a flipside perspective many would not normally come into contact with. It challenges a concept of one world government and other "official" stances. Breeding that type of skepticism and open debate by posing questions on topics which are neglected within mainstream society should be classified as an impetus of progress and change.
I think open dialogue and discussion on centralization versus decentralization may be one of the most pivotal and controversial topics we'll see in our day and age. There's nothing negative which can come from the idea of decentralization. All we can have is more information and knowledge being distributed perhaps where it is needed the most.
Decentralized blockchain doesn't exist. They are all controled by a few people or at best a few groups of people. If government wanted to control them it would be trivial to do so. Or if you happen to live in China, it is trivial to do so.
The historical ignorance of the claim that "all of the major plots aimed at depriving people of rights and freedom are heavily centralized in origin" is mindblowing. Without a strong central authority there wouldn't be any civilization at all. You can argue that we traded in some of our freedom for a lot of prosperity. But personally I don't find foraging for food in the forest whole day and then dying from a cold liberating.
Decentralization is not without negative sides. Most obvious is tragedy of the commons, without an authority to oversee a common good the shareholders will just use it up until destroyed. Less obvious are the threat of local decentralized area getting hijacked by a few people, productive inefficiency as centralized system employs economy of scale, growing wealth disparity between different regions and increased complications when organizing region or nationwide efforts.
If we are talking specifically about bitcoin, its design flaws have been discussed in much lenght here. Main problem is: when mining no longer creates new bitcoins an entity with a lot of money, say a central bank, can offer to mine transactions for free or to even subsidize users to use their service driving all other miners into bankrupcy. When they are the only miner they can choose not to process transactions of people they don't like effectively killing them as in 2140 everything will be on blockchain or similar ledger.