Shylock agrees to do business with Bassanio and Antonio, but he says he won't eat, drink, or pray with them. This seems a bit rude. When Antonio approaches, Shylock says that he hates Antonio "because he is a Christian." At this point, it seems that Shylock's problem with Antonio is based on his being a Christian. But then he adds that he hates Antonio for lending out money with no interest. Shylock claims that this practice of lending with no interest drives down the interest of other businessmen (Shylock included). He also claims that Antonio has insulted him for participating in usury (lending money with high interest). Shylock says "Cursed be my tribe" (his fellow Jews and ancestors of Israel) if he would forgive Antonio for insulting him.
Antonio never lends or even borrows money in which interest is involved. After initially agreeing to do business with Bassanio, Shylock backtracks and asks why he would lend money to someone (Antonio) who just last Wednesday was insulting him in the Marketplace. Shylock comes up with the plan to take a pound of Antonio's flesh if the debt is not repaid on time.
From this information, some conclusions can be made about Shylock, but nothing definitive in the sense that Antonio is the good guy and Shylock is the bad guy. Shylock does hold a lot of animosity towards Antonio and this seems to be personal and a matter of religion and/or culture. But Antonio says the feeling is mutual and that they don't have to be friends in order to conduct business. So they are both guilty of racism (race in terms of Jewish and Christian culture). Shylock appears to be the greedier of the two since he charges high interest on his loans whereas Antonio charges no interest. But then again, it is Shylock's money and his choice to charge interest. Shylock's plan to take a pound of flesh if the debt is not repaid seems barbaric but he claims it is all for fun: a "merry sport."
Shylock is a complex character. He certainly has his bad traits, but if he has been mistreated as he says, simply for being Jewish or for being a shrewd businessman, then the reader might sympathize with him. Note that in this scene, Antonio tells Bassanio that Shylock will quote scripture like a devil in order to make his point. One might get the sense that Shylock's ways are devilish but also come to the conclusion that Antonio, Bassanio, and others categorize Shylock as a devil regardless of his behavior. Just as Shylock hates Bassanio for being a Christian, it seems that Antonio hates Shylock for being Jewish. Shylock is a complex character. First time readers might be surprised to find that they will sympathize with him and condemn him at the same time.