Regarding the requirement that Shylock convert, those in Shakespeare's audience who felt close to the Roman Catholic church would surely have sympathized with Shylock as, at the time, all were required to attend the government sponsored churches.
Prejudice is mainly antecedent or occurred before the action of the play. Shylock's speech that begins "Signior Antonio, many a time and oft"(1.3) is one indication. Shylock's vexing aside that begins "How like a fawning publican he looks! / I hate him for he is a Christian, / But more....." therefore evokes the history of prejudice and atrocity against Jews. The latter passage also recalls Romeo's "Here's much to do with hate but more with love"(ROMEO AND JULIET, Act 1, scene 1). Also in Shylock's aside is the phrase "ancient grudge." This phrase also is found in the Prologue to ROMEO and nowhere else in Shakespeare's work. In the criticism we find Portia's "If he have the condition of a saint and the complexion of a devil"(1.2) and "Let all of his complexion choose me so"(2.7) are noted. Editor John Andrews(Everyman edition) wrote that "Complexion was often used to refer to a person's psychological makeup, the complex(admixture) of a person's humour's." So, it is not clear what Portia means and as she speaks disparagingly of the other suitors, one might wonder if she is saying these things, in part, because she has already decided whom she would prefer to marry. And thus there is much to consider and study regarding the matter.