The Great Wall of Food
Food is a great social lubricant. ‘Breaking bread together’ is a Christian expression, but the concept applies in every tradition with which I am familiar: it is one of the most effective and efficient ways to bring people closer. The flip-side is that food can also be a very effective tool for segregation and isolation.
Dietary restrictions are imposed for various reasons such as, amongst others, temporary or permanent health condition, severe allergy, fashionable food intolerance or religion. Only the last reason applies to a collective of people who identify with one another through an institution and its tradition and codes.
Codified prohibition of certain ingredients, such as products of certain animals or animals generally, places tangible hurdles to deeper and free social interaction by placing restrictions on what sort of food can be shared. Of course, it does not prevent people from outside of a given collective to share a meal with those that belong to the collective. However, it does demand that participants make efforts and provisions that are normally not required amongst their respective peers. Therefore, it makes social interaction more difficult and less spontaneous. Whether by intent or by accident, it is exclusionary.
It is subtle but effective because it is always easier to break bread with those who share the same constraints.