Lord, there is a mighty long list of sources and discussion about it here
http://en.wikiquote.org/wiki/EuripidesIt has been attributed to the ancient Greek playwright, Euripides (d. 406 BC), but the wiki scholar says that's wrong--it's a much older bit of wisdom that has been stated in various ways--none as succinct and elegant as the above--down through the Ages, all meaning approximately the same thing.
This is an interesting alternative:
Nor do the gods appear in warrior's armour clad
To strike them down with sword and spear
Those whom they would destroy
They first make mad.
Bhartṛhari, 7th c. AD; as quoted in John Brough,Poems from the Sanskrit, (1968), p, 67
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As part 2 of the Daily Kos narrative reveals, the golpistas tried to allege that Zelaya is "mad" (had lost his mind). (Cuz they couldn't imagine one of their own--a member of the aristocracy--genuinely seeking the good of the people.)
But the quote is more pertinent to the golpistas themselves. They are mad to think that they can govern the people of Honduras--who have caught the fire of real democracy in their hearts--with martial law--brutality, violent repression--and phony elections. That is the real madness. They have been wrong and illegitimate from Day One. Yet--driven by ambition, greed and their U.S. advisers--they persist with their lies and "nazi boot" methods though the Honduran people and all of Latin America (the real democrats of our hemisphere) oppose them. They are like "Macbeth." They will have a bloodbath before they will give up their unseemly power.