It is many things, but it's not robbery.  Social Security is a form of social insurance.  Do you always get out of an insurance policy what you put into it?  Is it robbery when you don't?  Of course not.  Is it robbery, for instance, when someone dies at 64 and never gets a dime from Social Security?  If so, who is doing the robbing?  Is it the little old blue-haired lady who lives to 100 and gets paid way more than she put in? 

The risk (in Social Security) that current workers won't get out of it what they put into it is a function of how the program is structured.  Current workers paying into the system pay the benefits of current beneficiaries.  If there are less workers and more beneficiaries, which is projected to be the situation for the next several decades, the math is simple-- all else being equal, benefits will decrease.

If anything, the problem is that people such as yourself would consider any benefit cut or social security tax increase as a manifestation of government "robbery", and the politicians don't have the spine to stand up to you and do what is necessary now to ensure that future retirees receive a full benefit.