That's not the point either of us are trying to make, though. Can Bitcoin be used to mask the source or destination of money? I think the answer is an obvious: "yes" considering one of its most prominent use-cases is exactly that.
And if the answer is an obvious "yes", then the whole thing about "immutable ledgers stop governments from spending money sketchily!" is obviously incorrect.
We already know, to the dollar, how much the black budget in the US is. The question was: is that money being used by politicians to enrich themselves? Bitcoin was offered as a solution. It is not.
That's an issue with the concept of a "black budget", not the payment mechanism.
The government corruption bitcoin stops is really bank corruption, but the central banks (including the fed) work hand in hand with the governments (control them in fact), so it's a kind of joint effort.
The corruption works like this:
When the Fed was formed in the early 20th century, it came to an agreement with the government to be able to print off unlimited amounts of money, providing it was in the form of loans and under the agreement that it would destroy the money when the loans were repaid. All under the Keynesian guise of "elasticity of money". The fly in the ointment is that the banks can charge interest on this money they print - if they didn't it would be a free-for all, because interest is what disincentivises debt.
What this led to was the doubling of the money supply every decade for the last 100 years, as the banks are incentivised to lend as much money as possible.
Each time you double the number of currency units, the total value of the money is diluted across double the number of units and so the value of each unit is halved. If you do this too quickly, people lose confidence in the money and you fall into hyperinflation, but if you throttle it just right, they don't catch on. It helps that the value of consumables (cars, food, toothbrushes etc) goes down by around 5%/year due to technology-driven manufacturing efficiency gains. This means that they can devalue the currency by 5% each year without prices going up. They then devalue it by a further 2% or 3%, simply because they can. This 2% or 3% is the CPI that's reported.
By holding interest rates lower than the free-market rate, banks both gain a monopoly on lending, and also ensure that people are incentivised to take on more and more debt - even though the money is destroyed when an individual debt is repaid, the total debt continuously increases.
The outcome of all this is that every year, the banking system is charging interest on every single dollar, euro, pound etc in existence. And it printed them all out of thin air. This has given it more power than you can even imagine and leads to all kind of evil and corruption. What's the best way to lend money? Start a war. Even better if it goes on for years and you can fund both sides...
It also results in the "Cantillon Effect" - an enormous transfer of wealth from the poor to the already rich without anyone noticing until it's too late.
This is because the newly printed notes take their value from all the existing currency units i.e. the value in the money in your pocket/bank account/pension/wages is being sucked out into the new notes they print off. You could bury your money in a concrete bunker a mile underground and they can still steal it. If you don't get a 7% nominal pay rise each year, you're actually getting a pay cut.
I highly recommend reading "The Creature From Jekyll Island" by Edward Griffin for all the history and details. This is a global problem.
The message in Bitcoin's genesis block reads "The Times 03/Jan/2009 Chancellor on brink of second bailout for banks."
Bitcoin's purpose is to shutdown the central banking scam, and is probably the only thing that can stop global domination by the bankers. Because its supply is hard capped, the more fiat currency the banks print, the more the price of bitcoin goes up. Over time it becomes more and more attractive as storage for large amounts of value. See Thiers and Greshams' laws for the result.
People worry about an AI machine taking over the world (https://www.youtube.com/watch?v=tcdVC4e6EV4), but its already here in the form of large human systems - an organisation with hive intelligence whose overall reward system is to make as much money as possible and a constraint of keeping the people happy (it does this largely by deception). And we gave this monster a money printer.
I'll leave you with a quote from F.A.Hayek (nobel prize winning economist who wrote "The Road To Serfdom" back in the 40s - he saw this coming):
"I don't believe we shall ever have a good money again before we take the thing out of the hands of government, that is, we can't take it violently out of the hands of government, all we can do is by some sly roundabout way introduce something that they can't stop."
https://www.youtube.com/watch?v=CBIidtaUCzs
And if the answer is an obvious "yes", then the whole thing about "immutable ledgers stop governments from spending money sketchily!" is obviously incorrect.