I grant you all of the above, but the stated reason these people are 'protesting' -- defense -- happens to be one of the only federal government programs spelled out in the Constitution.
And the numbers assigned were strictly NOT to be used for identification purposes. There were a few Senators which held out for that particular stipulation.
I suppose some of them were even thinking at the time, "mark of the beast", or generally opposed to giving too much power to Federal (or State) Goverment over individuals. But we are slowly losing that battle, it seems... Just recently (within the last 2-3 yrs) the State of California recieved "correction" from the courts for their requirment that S.S. numbers be given in order to recieve a driver's license. Now, one need not give their #. That "judgement" sets good precedent, I think. But the State of CA still requires Social Security #'s on other licenses. Must one "take them to court" for each and every breach of Federal Social Security guidelines? It looks like that is the case.