By making use of Blockchain technology for everything, global control will be enforced as it's much easier to track every single transaction made worldwide. Those transactions will not only involve money, but also transfer of ownership, certificates of birth, driver's license, and other services within the global Blockchain system. This may sound crazy, but if you look at the current situation where many Banks and governments have become interested in the technology, it shows us that it will be implemented in every area worldwide within the not-so-distant future.
You don't need blockchain to do any of that, and if we are talking about centralized entities, blockchain doesn't make any difference at all.
It really does. Public/open blockchains are much more transparent than legacy banks. There is all sorts of legal red tape for government agencies to surveil citizens (at least in western countries). If governments could get people to use KYC-linked blockchains, people would be offering them all their financial activities on a silver platter. No need for court orders or grand juries or subpoenas.