The themes of reality and appearance, love, deception, and honor clash in these few lines.
Act 4, scene 1 of Shakespeare's Much Ado About Nothing is set in a church, on the occasion of the marriage of Hero and Claudio. This was intended to be a public declaration of their love and the beginning of their life together.
Unbeknownst to Hero, Claudio has been deceived by Don John into believing that Hero has been unfaithful to him. Rather than simply trust Hero not to have betrayed him or question her regarding the apparent infidelity at the time it supposedly occurred, Claudio waits to take his revenge against Hero at the wedding.
Claudio publicly disavows his love for Hero, refuses to marry her, and challenges her to live up to her name. Hero tries to defend herself against Claudio's charges of infidelity, but she's far too overwhelmed to offer any defense. Claudio views Hero's inability to defend herself as a sign of her guilt, which affords him the opportunity to play the victim of Hero's supposed infidelity and wallow in self-pity and a paroxysm of antitheses.
CLAUDIO. O Hero! what a Hero hadst thou been
If half thy outward graces had been placed
About thy thoughts and counsels of thy heart!
But fare thee well, most foul, most fair! Farewell,
Thou pure impiety and impious purity! (4.1.103-107)
Claudio melodramatically vows never to love again—which is something he didn't do very well as it is. Claudio was in love with his image of Hero, not with Hero herself, and when the image was shattered—at least in his own mind—all he could do was assuage his own hurt feelings, wounded pride, and stained honor at Hero's expense.
CLAUDIO. For thee I'll lock up all the gates of love,
And on my eyelids shall conjecture hang,
To turn all beauty into thoughts of harm,
And never shall it more be gracious. (4.1.108-111)
Leonato, Hero's father—also wallowing in self-pity, and without a thought for Hero—feels utterly dishonored by Hero's supposed infidelity and deception and wants only to escape the humiliation that he apparently can't endure.
LEONATO. Hath no man's dagger here a point for me? (4.1.112)
Hero, the true victim of Don John's deception, falls to the floor in a faint. Only Beatrice, and later Benedick, show any concern for her.
BEATRICE. Why, how now, cousin? Wherefore sink you down? (4.1.113)
Don Pedro, Don John, and Claudio—the true perpetrator of a deception, and the self-anointed victims of Hero's supposed deception—sweep out of the church in self-righteous indignation, leaving chaos and a broken-hearted, nearly-dead Hero in their wake.
In parting, Don John offer a cynical, sarcastic, unfeeling assessment of Hero's condition, a condition that he himself caused.
DON JOHN. Come let us go. These things, come thus to light,
Smother her spirits up. (4.1.114-115)