It isn't Social Security and Medicare that are killing other social programs, but Republican refusal to support them. The ratio of public debt to GDP is roughly stable for the next decade. If we begin making cuts now, whether in Social Security and Medicare, or in other outlays, we will slow the recovery. That will only worsen the debt ratio over the long term, and at a depressed level of economic output. Republicans do resist higher taxes, but at times Democrats have prevailed in raising taxes on the rich -- with the full support of the voters. President Clinton managed it in 1993, and even President Obama, though he settled for too skimpy a bargain, got Republicans to vote for a $630 billion tax hike on the top one percent last January. Faced with a choice of cuts in Social Security and Medicare or tax increases on the wealthy, polls show that most voters opt for the taxes.
The sequester, and all the sequential sequesters over the next decade, deprive Democrats of the resources that they need to be, well, Democrats. Obama can proclaim big, bold initiatives as he did in the State of the Union Address, but they are all mere gestures -- because there is no money to spend on any of them, thanks to the bipartisan obsession with budget cutting. Even worse, Democrats end up colluding in eviscerating very popular and necessary signature programs like Medicare and Social Security, which literally define the core differences between the two parties. So by 2016, and even by 2014, nobody will much remember who was more at fault in the sequester battle of early 2013. The voters will be looking at their own economic situation, and it won't be pretty.
President Obama and the Democrats' willingness to accept cuts to Social Security in the form of the gimmicky "chained CPI" right after an election where no candidate for federal office campaigned on it shows that the Right's long-term project of undoing the New Deal marches on despite the electorate's wishes.