First of all, it was 4th grade that it began to be difficult for my son.........opinions simply came "out of the woodwork" as opposed to the Primary years, so that part seems normal to me, although it doesn't make it right. Your son needs to be confident within his home about who he is, no matter what his religion.
I really want to commend you for being a part of your son's classroom. It is truly important, in my opinion, and even though he is getting older, I bet he truly appreciates it.....of course, until now.
I have to be honest, I don't know much about the game :o) But, I find it odd that you would go in and play any sort of game relating to your religion, and especially odd that the teacher would allow it. Unless, of course, it was cirriculum related and you were discussing different religions, and you were a guest speaker. In any case, I would be upset if my son were in the class, and the Jewish religion game was all that was allowed and focused on that week.
If I were in your shoes, I might try to "redeem myself" and show that just because you are a Jewish family (in their eyes, not mine) you can still have fun (and be smart). Maybe you can go in there and lead a different game.....maybe a fun "math facts" game with a multiplication race......it's non-religious, cirriculum related, and it shows fun and it will show your son being smart :o) At least, the other Jewish boys I've known from my sons class were all really good at their math facts , and I'm sure yours is too :o)
For now, I would explain to your son that your game was misunderstood, and the attitude's will go away, so just be patient for now. I wouldn't try to do anything else except for redemption in an innocent way.
In my 10 years of helping in the classroom, nobody has ever been asked to come in and do anything "religous" in a public school, so this is odd to me. I mean, we are in a place of our government that they are considering changing the Pledge of Allegiance, so why would ANY teacher allow any sort of religous conflict in his/her classroom is beyond me. That will just open a can of worms, as you are discovering.
Just let it lie......don't persue anything except for redemption that you are a regular fun family just like those in the class.
~N. :o)