I think that whilst GPS is an excellent tool, it should be remembered that it can be switched off at any point by the authorities.
So can ground based navaids, which leaves IFR OCAS exactly where?
Your comments are applicable to the "VFR-only PPL" world only, where one is supposed to navigate with a map+compass like one did in WW1. But remind yourself of the min PPL vis figure, and show me how you do map reading in that.
That's before one gets onto the likelihood of the USA actually switching it off and crippling itself economically.
that we have no right to GPS services (in fact the use of it should be looked on as a privilege rather than a right)
A student of Lord Denning, perhaps? 
BTW, SA errors are irrelevant to enroute flight. It was something like 200m which is way better than with any other method. And SA was stopped about a decade ago, and never reintroduced - not even after 9/11.
I agree about amateur UAVs but while that technology has appeared on the retail model aircraft scene only about 3-4 years ago, it was possible long before that. Yet nobody has used it for terrorist purposes. I wonder why? The payload you can carry is very small. A terrorist cell (they rarely work alone) is a significant operation, which needs organisation and needs funding, and they are not going to waste their time and risk getting exposed by doing nuisance stuff like that.
The thing I find funny about these forum debates is how some people are happy to chuck away all the capability we have picked up in recent years and go back to living in the caves. Maybe these people just happen to be very vocal.