Mike B,
In my 50 plus years of playing poker, there was a protocol at the showdown that was understood by all. It went like this: If you were the first bettor on the final betting round, or the last person to initiate the last raise, you showed your hand first. There were many occasions when a player was bluffing and once he was called, he would surrender his hand to the muck and say "you win!" He new he was beat and elected not to show his hand. He was "caught bluffing" one of the consequences was showing his "bluff" if a request were made by one of the players in the hand.
The principle (I would say) was: any player that called all bets "paid" for the right to see any called hand at the showdown. I don't know when, or why this changed. I understand that the game has evolved and change is necessary. However, I believe there were some changes that were not for the better, and this is one.
The games I speak of, were primarily cash games. Tournament poker involves all participants so I understand that it is necessary to assure that the best hand wins. Therefore, I suggest that the TDA should seriously consider taking the option to muck away from any player in for all bets at showdown.
Mike, I'd also like to comment on what you wrote: "players mucking face down at showdown lose any right they may have to ask to see a hand that otherwise they do not have an express right to see." Among other reasons, this language is intended to encourage players to table their hand at showdown for as you say this is the desired outcome: the membership affirmed that we want to encourage players to table at showdown to increase the probability that the best hand wins.
If we want to encourage it, why not just make it a rule? As far as a player that mucks, losing the right to ask to see another players hand

What does that accomplish?
I guess I just don't understand how asking to see a called hand is any different than being forced to table my hand because a player is all-in