1. A stereotype is a fixed belief-image-notion about people or things that seem different and we do not bother to check if our belief is true to life. 

2. There is a breach of communication and dividing walls are erected.

3.1 The communication is definitely problematic and cannot lead to much of understanding. It is a matter of personal identity and no one would like to be viewed solely as one thing. Seeing the whole picture of a person requires qualities of active listening, a great sense of humour to see beyond the surface, be ready to re-evaluate your views and whatever else works.

3.2 The ineffective communication has started earlier on before the offering of shrimp at the dinner party. One of the speakers has failed to notice that his fellow speaker wears a kippah-the traditional cap of Jewish people, mainly worn by men- https://en.wikipedia.org/wiki/Kippah and probably ignores that Jewish people follow certain rules as regards their food. Fish or seafood to be Kosher it must have fins and scales. Of course, you cannot know the Kosher Fish List.http://www.chabad.org/library/article_cdo/aid/1182104/jewish/All-About-Kosher-Fish.htm This is one thing and another to assume that Jewish people are stingy. Effective communication can occur if both speakers transcend the limits of their own cultures and engage in a true dialogue.