Why is Shylock's "Hath not a Jew..." speech important?

In this speech (III.i.48-66), Shylock offers a furious yet relatable explanation of his desire to enact vengeance against Antonio by claiming his bond and taking a pound of flesh from Antonio's body. Shylock is angry that Antonio has "disgraced me, and hindered me half a million; laughed at my losses, mocked at my gains, scorned my nation, thwarted my bargains, cooled my friends, heated mine enemies" (49-52), all because of Shylock's religious and ethnic Jewishness. Shylock has also just lost his daughter Jessica, who has eloped with the Christian Lorenzo and stolen much of Shylock's fortune. In this speech, Shylock stresses the similarities between Jews and Christian: both experience the same physical and emotional forces. Treating Jews like “dogs” rather than human beings will rightfully elicit their vengeance: “If you wrong us, shall we not revenge?” This speech marks Shylock’s abandonment of mercy and compromise in favour of violence and vengeance. This is a tricky speech because to a modern audience Shylock seems entirely justified. Antonio has been antisemitic and cruel to Shylock, and the loss of Jessica to a Christian layabout makes Shylock's desire for violent revenge against the Christian Antonio understandable. It is important to remember, however, that Shakespeare's audience were themselves antisemitic. While we might sympathise with Shylock and think Antonio deserves to have the pound of flesh carved from his body (a condition to which he agreed should he default on the bond), for Shakespeare’s audience, Shylock’s rejection of spiritual mercy in favour of bodily vengeance would not have been seen as justifiable. Shylock is far more sympathetic, however, than many usurers or antisemitic stereotypes in early modern drama. One of the most notable aspects of this speech is that it details the shift of Shylock’s primary motivation from money to vengeance. Despite the loss of his fortune at Jessica’s hands, even when Shylock is later offered "thrice thy money" (IV.i.231) to let Antonio go, he refuses. This prioritisation of vengeance over wealth humanises Shylock, but his commitment to vengeance against the Christian Antonio would not have been celebrated by an antisemitic Shakespearean audience.