To make a long story short, one kid, Kyle is a Jewish lad. Cartman is a loud, arrogant guy who hates Kyle and makes fun of him for being Jewish constantly. Ever since the Passion, Cartman has been really mean towards Kyle and insisted that Kyle go watch the Passion so he could see the "truth" of how much Jews are bad. Kyle sees the movie in all its gory glory and is horrified at what the Jews did (it should be acknowledged that there are many debates here as to the historicity of the Bible, how faithful Mel was to the Bible and how faithful Southpark is to The Passion, and that the people that actually crucified Christ in the bible were the Romans who were fearful of a Jewish uprising). He immediately admits to Cartman that he was right. Cartman immediately feels very worshipful towards Mel Gibson and so creates a fan club. Cartman believes this movie is an attempt to make people aware of how evil Jews are. So he arranges for everyone who likes the movie to come and march. Naturally a bunch of Christians show up and they believe that Cartman's interpretation is like their own: that the movie is a depiction of the love of their Savior. When Cartman (who is dressed like Hitler) has them march down the street chanting something in German that sounds like it is talking about removing the Jews, they believe it is Aramaic, and innocently march behind him. This episode also contains Mel Gibson running around the screen in underwear, waving a sword, driving a semi truck like a mad man and speaking Klingon...but that doesn't really go to my point at all. So in the end, Cartman saw what he wanted to see: a film which made Jews look bad. Kyle saw what he was afraid to see: that the death of Christ was the fault of the Jews. The Christians also saw their own interpretation of the film: a piece which though gory, shows the love of God for humanity in that he was willing to die for us even while we were his enemies. One last thing should be mentioned. During the episode, Kyle and Cartman's friends Stan and Kenny go to see the movie..and they hate it. They saw two hours of torture...and nothing more. They try to get their money back...from Mel Gibson...hence the madness and dancing around in underwear mentioned above. :)
So after watching all that I related what I saw to what has happened in the real world in response to this film.
Christians predictably flocked to the movie and many of them loved it. They are sick of rejection, mockery and a society which seems to exclude them (more on this later) and a majority of them will chase anything which doesn't try to make them look foolish. They flocked to Michael Behe when he wrote a book which creates a very good case against Darwinian evolution even though Behe is not himself a Protestant. They usually flock to anyone who smiles at them. Christians brought their interpretation of the Bible and it fit in just fine with the movie. This is much lke what happens in South Park.
More important is Kyle's reaction which is much like the reaction of many Jews upon (and in fact, before) seeing the movie. The Jews have faced and continue to face many horrors and have been persecuted by Christians for the death of Christ. They feared that this would happen again. I'm not surprised that when they saw this movie that they saw it as anti semitic. I'm also not surprised that upon seeing this South Park episode that I found it to be a little anti-Christian. I'm sure you're not surprised either.
The most fascinating was Cartman's reaction, which is much like the reaction of Muslims with this movie. He, and they, saw what they wanted in the movie much like the Christians. Many Muslims hate the Jews, and it has been reported that one of the reasons they love this movie so much is that Jews hate it so much. I have little doubt that many Muslims have speculated a future that is much like the Jews did: that perhaps this movie would move American sentiment against the Jews..something which would be very helpful for the Palestinians.
One more group had an interesting reaction. Secular people who do not believe that the Bible is either spiritually true or historically accurate saw a movie which was merely 2 hours of gore and torture. They do not buy the Jesus thing, that he died for us. The message means nothing to them...all that is left is blood and gore..and the possibility of a backlash against the Jews. Mel's point is lost to these people in a sea of blood.
I don't really have a conclusion. I'm sure you can furnish one of your own. :)