Mike,
I am all for the dealer taking charge at the showdown. There are specific procedures that must be followed. The incident in Barcelona was a good example of the dealer taking charge of the situation. The dealer asked the initial bettor to show his complete hand (both cards), instead, he showed only one (the king) and actually slid the other into the muck.
What I consider to be the duties of a dealer at the showdown; a) Ask to see the cards of the player who initiated the last bet or raise, first. Example "sir, I need to see all of the cards before I can read your hand." b.) Stop any opposing player from showing their hand until the first hand is properly tabled (face-up horizontal on the table). c.) Muck all discarded hands, immediately. d.) Kill the losing hands and push the pot to the winner.
There will always be exeptions to the normal process that are accepted and prefered. Example; Player A checks, Player B checks (holding the "nuts") hoping that one of the other players will bet, so he can check raise. All of the remaining players check (to the disappointment of Player B)...so, even though he is not following the correct order of showdown, it is in the best interest of the game, to not waste time by turning over the nut hand and get on with the next deal.
That's my vote.
Nick C