Yglesias calls for it:
I don’t think we should cut Social Security benefits. But if we are going to cut Social Security benefits, I think it doesn’t make sense to do what the Obama administration has done and make “No current beneficiaries should see their basic benefits reduced” one of the bargaining points.
E.G. at DiA sympathizes but expects "changes to Social Security benefits to be written to affect future beneficiaries only" and explains why.