Thank you for reemphasizing this point. This debt is just as legitimate as that owed to investors in T-Bills including Chinese, Japanese, American, and other investors in government securities. A major factor in the early turn of Social Security receipts from surplus to deficit was the long term high unemployment rate. While our government is clearly on an unsustainable financial path, demagoguing the Social Security program is not going to solve the spending problem. Like it or not, a major segment of the population participated in the Social Security program for all of their working lives with the expectation of a certain return and they do not have the time left to go in another direction. They are not going to just lay down and die.
The reality of SS is that the contributions you make into the program don't belong to you. The Supreme Court decided this, Flemming vs Nestor, some time ago. Moreover, Congress can change the rules anytime they want, e.g., in 1983 they changed the age for full benefits from 65 to 67.
Someone could pay into SS for 50 years, die the day before starting to collect benefits, and not receive a dime except for a small burial allowance. It is not a pension scheme nor does one's estate have any claim on one's contributions.