Ummmmm ..... You do remember his $4 trillion grand bargain with Boehner, right ? The one that Cantor lit on fire ?
The plan that was merely going to reduce annual deficits, as opposed to eliminating annual deficits, yet was "sold" (unsuccessfully) as a debt reducing plan?
While I am against a Balanced Budget Amendment, because there are emergencies that might require spending extra in one year or two years, I am against a ten year plan that in the best year of the plan still leaves our government incurring a $300B deficit.
Hell, even if we grant Obama that $4T would have been cut, due to interest payments on our debt, the actual cut would have merely been around $2.5T by the end of FY2020 (in other words, we would still be dealing with over $13T in debt).
This is why entitlements need to significantly overhauled; medicare and medicaid need to be significantly overhauled; education needs to be significantly overhauled; defense needs to be significantly overhauled.
The system is unsustainable and that means that drastic measures need to be taken. Does this mean that promises that have been made to the American people must be broken? Yes. Is that unjust? Yes. It is bad; they are promises the government ought not to have ever made; the breaking of the promises ought to invited skepticism from the populous with regard to future promises this government makes.
That being said, if I make a promise to you that I will murder x and I break that promise, then I am committed an injustice toward you. You might have made plans that relied on me murdering x (maybe you were going to inherit and you jump the gun and take out a big loan). Ought you refrain from or be more cautious in accepting my promises in the future? Of course.