How is Shakespeare anti-Semitic?

To explain—but never excuse—Shakespeare, it's important to understand that anti-semitism was common in Europe from well before his time up through the early part of the 20th century. That said, the most famous portrayal of anti-semitism in Shakespeare is the money-lender Shylock in The Merchant of Venice. Antonio, a protagonist, illustrates Renaissance anti-semitism when he spits on Shylock. Further, Shakespeare portrays Shylock as money-hungry and unforgiving, once common stereotypes of the Jewish people. Shylock famously demands a pound of flesh in repayment of a loan, insisting on it even after he is offered a repayment amount of twice the loan. Shakespeare depicts this lack of mercy as Jewish (in those day cutting a pound of flesh could easily have been a death sentence, given the state of medicine). This stubbornness on Shylock's part leads to another famous line from the play: "the quality of mercy is not strained," with mercy depicted as a quality associated with the "superior" Christian faith.