Interesting discussion...
I'm going to throw a real monkey wrench in your whole polarized world here. Maybe the very nature of the play is adding to one of the central themes, that opposites are really just two extremes of the same essence. Let me explain. Hot and cold are both temperatures, up and down are both directions. Without yin, there is no yang. So, if you take this into the play, both Jew and Christian, while portrayed as opposite poles, are still human. Antonio and Shylock, while enemies, are both merchants of Venice. Belmont and Venice, though apparently worlds apart, are still dealing with the same issues of love, bonds, money that make us human. In other words, you can't have the experience of one extreme without at least an understanding of the other side. I know this is going a little ToK on you, but may be relevant to the tragedy/comedy debate, too. Can we understand the comic without knowing how to cry? And, can we truly feel the pathos of tragedy without also having laughed before? Maybe the fact that this play defies easy categorization is in a sense a comment on the play's characters; Antonio, Bassanio, Portia and even Shylock also defy easy labels. Is Portia the "poor little rich girl" or the cunning imposter who saves her friends, and isn't it possible she is both? Is Shylock the justified victim of a prejudiced society, or the really evil villain, and is it possible he is both? Chew on that, amigos.