FB
I comprehend the scenarios you offer but I restate what I believe.
GPS is here except in the event of major war. Turning it off is improbable otherwise, too much dependency. Although, to be fair, in the WAAS/GBAS debate I understand some sovereignty issues with MSAT. Different argument.
GPS already has failures, thus the removal of TSO129a from the ADS-B platform. I was uncertain re this, the data are persuasive.
Yes, GPS can be used by terrorists. I use a knife with my steak, the same knife can be used to terminate me. Tools have various uses, do we allow the 1% factor to overcome the good.
ADS-B is a surveillance mode resulting from technological advance that allows ATC efficiencies and aircraft-aircraft efficiencies. I don't believe the arguments against overrule those for.
What is needed is rational debate on the inevitable and how to best manage it.