Miners should be able to easily detect erroneously high fees in the same way they detect transactions with too low a fee and also reject them outright. There is no philosophical argument required.
True, but due to the nature of the private sector this is unlikely to actually happen. As long as we use a currency which is trying to be decentralised and manages its transactions through rewards, many miners (especially the smaller ones) will continue to take these fees for themselves.
I don't even believe that Bitmain would have returned the fees if they didn't expect the miner to make the error public and potentially damage their image.
Private sector is made up of people; people like you and I in fact. The decisions come.down to people like you and I. I own a private company and I provide a service which I let people try free of charge before they commit to purchase it for a speified term. Even if people have paid for my service, I give refunds on request every time no matter when they ask even though I lose the transaction fees. My money is where my mouth is and I practise what I preach.