Americans say: “There are three things you never address at a cocktail party: sex, politics, and religion.” All three are perceived as private or overly controversial for an occasion like a cocktail party, as a metaphor for information interactions.
Discussion of religion and politics could make some people feel that you are either in agreement with them or opposed, feelings which could provoke tense conversations. Discussing sports, weather and family are considered to be safe topics with which to begin a conversation.