Our Responsibility as Hashem's Ambassadors

Moshe Rabbeinu warned that Makas Bechoros would come at "about" midnight, though Hashem struck at exactly midnight. The Gemara in Berachos says he was worried the Egyptian astrologers would miscalculate. But why would Moshe care what they thought, when within minutes they would see the plague arrive just as he said? The answer sets a standard for anyone who looks like a representative of Hashem. A newspaper article waiting to go to print, with a correction promised for tomorrow, makes the standard very concrete.