I'm interested in the argument line that would be "Ok, let's assume you are impeccably honest, infallible, and have unwavering integrity and unstealable secrets ... even under those laughable, impossible conditions, it's still a terrible idea because of the following..." and go from there.
The perfect recipient would still have to be sent backdoors from many creators. Many more people would be handling the secret, each one a target to be social engineered into handing it over. I imagine when a more typical backdoor is made, very few people even know it exists let alone know the key to open it. Mandate backdoors and everyone knows they exist so more people will work to find and crack them. They would be very high value targets. Once opened, a backdoor would take a lot of work and expense to be closed, if you even know it had been opened.
Yes, the whole idea is about as plausible as this april fools joke: https://en.wikipedia.org/wiki/Evil_bit ... but it's been put forth and implemented too many times for comfort.
Each time these silly systems like DVD-CSS broke down and became worthless or like DIVX, were widely panned and rejected by the consumer.*
Showing how this will always and forever be the case at a more fundamental level to stop trying this deadbeat idea with different gift-wrapping would be great.
* Even in MP3, you have bits 29 and 30 which are for copyright. What were they thinking? people would re-implement /bin/cp to look for that and fail if the bit is set? Really? AAC has something similar. silly.
Even with absolutely perfect systems, which do not exist in practice even when they may exist in math, the humans with the keys are the weakest link. Stolen credentials are the biggest cause of data breaches in enterprise web applications (according the the Verizon DBIR). And even for absolutely perfect humans with impeccable morals, which do not exist as no one is perfect, there is coercion in the form of rubber hose cryptography.
