The US dollar is self-funding when Congress creates it in the private sector. This means that it can never "go broke"; by extension, its programs and laws are similarly advantaged unless one interjects an artificial limit to them, such as a "fund" of Treasury debt.
No one "stole" the Social Security tax revenue or used it for other spending. That is simply how Treasury bonds function. The people paying the tax gave up liquidity/purchasing power in exchange for a promise to pay in the future. This had some application when we did that "gold standard" nonsense, but it is now just useful as propaganda to sell lower benefits.
Paul Ryan tried to pin down Allen Greenspan to agree with his privatization scheme. He should have not placed Greenspan under oath if he wanted agreement to his fantasy economics. Greenspan emphasized the need for "real resources" beyond the accounting of money, as he should have. It was quite obvious that Ryan didn't get the answers he wanted.
