I'm not sure if Bitcoin is that antagonistic that it was created to destroy the current economic system, the one which capitalists like Buffet have taken advantage of. Or it was simply created to be an alternative to fiat.
But be that as it may, you cannot expect these people who have benefited so much from the current system to show strong support for that which tries to disrupt such system itself. They have already made successful empires with this system.
That's correct, but one important point to consider as well is that Buffett is not only speaking for himself, but also for all the shareholders and stakeholders, among which are almost 400,000 employees. He might think that this is the best way to protect their combined interests. He might also really truly believe that Bitcoin / decentralized financial systems are trash. Now in his eyes it should absolutely be trash because outrageous rent-seeking at close to zero marginal cost becomes significantly harder in openly accessible systems. Buffett wants systems that generate revenue, ok, I get that. But for how long did banks not innovate and instead played the cat and mouse game because there was no competition on the horizon at all?
Revenue from transaction cost was the easiest money banks could ever earn. Only later on when big scandals happened and they fucked up big time here and there came stronger regulation into play, but it still was pretty much the same process for banks to transfer either 10 USD or 10 mio. USD. Yet they took a more or less flat percentage cut of the sum transacted. Closed doors on the weekends, no service after 6 PM and before a AM and so on and so forth.
With a competitive system that never sleeps, the banks realized they have to get their ass moving and they can't offer their services at too expensive prices in order to not create further incentives for the competition to innovate even harder.
Among the most important characteristics of Bitcoin is that it didn't have to get a banking license, a process that used to be so hard that its only goal was to preserve monopolistic rent-seeking banking infrastructure for the long-term. While banks complained about some regulation, they wanted harder regulation wherever it led to insurmountable barriers to entry for potential competitors like banking start ups or financial applications taking business away from them. This has of course changed significantly, not least because the whole world went mobile.
Bitcoin does not need permission to co-exist. People are free to choose whether or not they want to use Bitcoin in order to either transact globally or just take some of their financial wealth with them no matter where they are going. Unlimited capital mobility is again something that takes away leverage from banks over their customers. They can't freeze your accounts nor put you under pressure in any other way they'd subtly love to.
And of course there is the competitive character of Bitcoin towards FIAT and that is something policy makers now more and more are forced to have on their radar when making important economic decisions. They are still doing whatever they want as it seems, but this is a question of time I suppose when Bitcoin as a system becomes such a viable alternative for the vast majority of the people around the globe that policy makers will indeed think twice before making their decision.