Already in the first scene of the, we can see how Shylock was prejudiced just for the fact that he was a jew. He was being stereo typed along with race. Some of them were being beaten up, some even thrown into the river all due to their race. Shylock was even spit upon at by Antonio when all Shylock did was to greet Antonio.
Throughout the whole movie, there was one event where we can clearly that Shylock was unfairly treated. When Bassanio and Antonio wanted to address Shylock they always say "the Jew". There was only one scene where I remembered him being called his real name and that was when Bassanio needed to borrow money from him. This is another form of Shylock being prejudiced against.
Another scene where Shylock was a victim of prejudice was the trial. When Shylock wanted his forfeiture of one pound of flesh, all the audience disagreed with him. Even when he gave his reasons for doing so, not only did no one agree with him, they jeered him even more.
It is understandable why Shylock insisted on having Antonio's pound of flesh no matter what. After all, Shylock has been putting up with Antonio's behavior for so long. Even when Antonio spit upon Shylock, he just stood on the same spot without any hint of retaliating. Also, since jews cannot own any property nor work outside the Ghetto, their only form of making money was to lend out money and collect back usance - a form of interest. However, Antonio always insulted him of his "job" but Shylock just left it as it is. That is why Shylock is so persistent in killing Antonio.
In the movie, one main theme was mercy. In the trials, Portia talked a lot about mercy. How Shylock should be showing that, how benefiting it is to the soul and how it is like and attribute of God himself. Despite saying all that, I think what she said was all a bluff. She talked about the greatness of mercy herself but did not practice it. After Shylock compromised to take the 6 thousand ducats, then down to 3 thousand and even not want the money at all in the end, Portia was heartless. Not only did she not let Shylock off without taking the money, she forced him to take his forfeiture and finally made him give up all that is left of his possessions.