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That is what I thought. Thanks guys! I guess the Elders fall under the "Those who are silent are presumed to consent" clause.
Interesting side note: The REG states that the discard ability targets cards in play by default. That needs changing, since there are discard abilities that target the hand.
And if you think of it, the Goliath/Wall of Protection reasoning is similar. Even though Goliath says "Opponent may present a new hero", it is Goliath's ability that is causing your opponent to choose to present a hero. Who makes the decision does not matter; where the ability comes from that allows the decision does. If your hand is protected from discard, you cannot negate Sinning Hand.