SS and Medicare not a Quid Pro Quo

In this election season I am seeing a lot on political ads saying that this or that group payed into Social Security and/or Medicare and so they have a claim on the system, therefore the Social Security and/or Medicare system must not be changed to help with the deficit.  But the programs are not a case where people voluntarily bough a specified future benefit.  Rather people where compelled to pay and they will receive what the democratically elected officials decide the benefit should be.  The programs have been changed before and they can be changed again.  There are no Guaranteed Social Security and medicare benefits.

Here is Ross Douthat on the payroll tax.