Re: "Outside the digital world, none of us would accept the proposition that"
Enter your house yes, through any means necessary no.
For instance they arent (yet) allowed to request/demand the keys to everyones house, in case they later need to pop in, with or without a warrant.
Whether the proposal is for a global decryption key, or decryption keys specific to each encrypted channel , the fact remains that if a 3rd party (be that the police, your local neighbourhood pedophile, facebook, a foreign state, criminals, your mom etc) has access to decrypt your data, then its no longer safe (because we encrypt to stay safe). If one of those 3rd parties has access then they potentially all do.
The takeaway from this should be that the different aparatus that we accept to limit our freedoms in return for greater safety (the police, the justice system, local regulations) must themselves be kept in check in order that they dont exceed their mandates (which they recently have gone to great lengths to do).