The rest of the Medicaid money (32%) goes to poor adults who can't afford insurance. I think that section of the spending is what many people find distasteful. But that is only if you look at half of the picture. We were paying for their health care anyways through bankruptcies and non-payments of medical bills. So reducing official spending on Medicaid for the poor doesn't help with the problem because we just pay for it in unofficial ways.
Our $19.85T of debt is quite manageable at the moment. That is 10% higher than our $18.04T of GDP. It is the equivalent of someone earning $100k having a $110K mortgage which almost everyone would consider to be quite manageable. Your point is correct though, that debt is growing faster than GDP and will one day become unmanageable. Obamacare, however, isn't the cause of the growing debt. The taxes in Obamacare are higher than the spending in Obamacare. So, getting rid of Obamacare makes our debt worse.
To fix the debt, we need to (a) promise less in the future especially on Medicare, Social Security, and Military spending and (b) tax more now to match the promises that we have already unfortunately made. Both are political suicide.