Leonato is upset and angry not at Claudio, but at his own daughter Hero. Leonato believes that the Prince, being the highest nobleman in the area, is incapable of telling a lie. Leonato believes the Prince, and thus Leonato believes that his own honor is ruined. The shame of a daughter, according to Renaissance custom, reflects on the entire family. Leonato becomes impassioned and irrational. In a lengthy speech, Leonato curses his daughter to such an extent that audiences today may find his words surprising or even shocking. But the reader should keep in mind that Leonato is desperate and is not thinking clearly.
Leonato's first response is to wish for his own death:
Hath no man's dagger here a point for me? (107)
To Leonato, death is preferable over a life of dishonor. And he also believes the same should hold true for his daughter. Hero has fainted from shock, and she appears lifeless. When Beatrice fears that she might be dead, Leonato's response is definitely a surprising one; for he hopes that his daughter truly is dead:
O fate, take not away thy heavy hand. Death is the fairest cover for her shame That may be wished for. (112-14)