Ezra Klein outlines the "pro-Social Security case for Social Security reform":

[Too often] the folks most resistant to reforming Social Security are also those most committed to its mission. Many of the program’s defenders are so concerned that conservatives will slash benefits now or down the road that they are afraid to open the pension plan to any reforms at all. I think they’re wrong.

Austin Frakt applies this line of argument to Medicare:

[E]very time someone suggests changes to either program it isn’t long before someone else trashes it in the name of protecting it from benefits cuts. It’s not necessarily an incorrect argument, not always. But if one is serious about preserving either program it can’t be an argument always and forever about every possible reform. If it is, it is essentially an argument for no reform. And no reform itself guarantees benefits cuts (see Don’s graphs).