I believe what FB is trying to say is that if terrorists were to somehow employ the GPS system in some sort of attack, the US might turn it (the constellation) off. His reasoning is, therefor, it would be short-sighted to base the entire aviation surveillance and navigation systems on GPS.
IMHO, I think he is correct insofar as; if there were some sort of large-scale, co-ordinated attack using GPS guided weapons against the US, they might indeed interrupt the signal. In much the same way as pretty much EVERY commercial passenger jet in the WORLD was grounded on 9/11. For a short time.
However, based on the RISK, should we not proceed? Well, was every passenger jet permanently grounded? Did everyone regret ever having passenger jets, thinking "they were a huge mistake"? No, we mitigated and moved on. If every aircraft in oz is being navigated and surveilled using GPS technologies, what would happen if they signal was interupted unexpectedly? Would everyone crash? Would anyone crash? No, there are mitigators. As has been stated (over and over), the surveillence aspect is covered in that ATC would revert to procedural control and primary radar surveillance ie. go backwards a few years- inefficient, yes, dangerous, no. Aircraft navigating- well, there are plenty of aircraft using only GPS already. Pilots are trained (hopefully) in what to do, and there will be other mitigators (retention of navaids etc). If you are a GA pilot wandering around without any idea where you are without your GPS, then your airmanship might be questioned. But will you immediately perish? No.
Mr. Binghi would have to agree, that the risk of the GPS signal being interrupted is minute. The reward for utilising ADS-B now is massive. Risk/reward? It's a no-brainer.
It doesnt hurt to raise things, FB, and now hopefully another perceived problem is given it's proper perspective and put to bed. Thanks.