Kosher vs Not Kosher Taboo

Hillel is a very unique agent of socialization, because it specializes in Jewish life.
The Rabbi of Hillel introduced me to Birthright, an all expenses-paid trip to Israel for 10 days. Like Hillel, the trip is an agent of socialization in its own. The difference between the two is that Birthright is not very religious oriented. It is more focused on bringing Jews to the homeland to experience and appreciate its citizens, landscape and overall culture. It is very secular.
On the first day of the trip, the Birthright Rabbi held some ice breakers for us to get to know each other. We sat in a circle and the Rabbi would ask us our favorite movie, holiday, sports team and whatnot, then each person around the circle would introduce themselves, followed by their favorites from the categories mentioned. The first category was food. I was a bit hesitant because my favorite foods at the time were all non-kosher. So I thought to myself, should I say tell the truth by saying lobster, or should I instead say a kosher food, and not rock the boat? I waited to see if anyone before me would say a non-kosher food, but nobody before me did. When it was my turn, I said: Lobster with melted butter. I didn’t know what to expect from my answer. Would there be some sort of harsh sanction, like people sneering or giving me dirty looks? Apparently not; not only did the group laugh and appreciate that answer, almost everyone whose turn was after mine mentioned a non-kosher product as their favorite food.
While speaking of non-kosher foods was embraced on a not-so-religious trip, I experienced a completely different reaction at Hillel. The Hillel Rabbi hosted a similar ice breaker game in honor of Lag BaOmer, a Jewish holiday. When the category was food, again I waited to see if anyone would say a non-kosher food before me. Again, nobody did. When it was my turn I said my favorite food was lobster with melted butter, like I had done on my birthright trip. Everyone in the room seemed appalled, and the Rabbi immediately went on to the next person. I laughed inside, but felt mildly ashamed. I should have known that the Hillel takes such matters seriously. But I don’t understand how having a different food preference than others can be a form of deviance. After that, nobody talked to me the same way they used to. I had blatantly told everyone that I am not an observant Jew.