As a historian or even an anthropologist, one could make the argument that being a vegetarian limits one's ability to understand other cultures. I, like you, am not a complete vegetarian. In fact, my diet is worse, but I do justify my eating habits. I refuse to eat pork, but eat grass-fed beef when I am making Persian food, and certain forms of chicken and lamb with other ethnic foods I consume. I also have a rule to eat any cultural food when I am traveling to another country or am a guest or have guests of people from another culture who eat food with meat. Food is such an important part of history. In many ways, it has a lot to do with defining one's culture. If a person is in a discipline in which he or she is attempting to understand a culture or wants to experience a culture, vegetarianism is nearly impossible. So, how you would respond a person like me who cares for animal welfare, consciously stays away from the worse meat he can, and eats it mostly for cultural reasons. When I do cook it (which is maybe once every two weeks), I try to be a responsible as possible.
Note from KBJ: Thanks for writing, Brad. Suppose you travel to a place in which cannibalism is practiced. Do you eat the human flesh served to you by your hosts? Suppose they eat feces, grubs, dirt, or vomit; do you partake? By your logic, you cannot understand them unless you do. And why limit it to food? There are other customs besides diet. Suppose your hosts offer you young women for sex, as occurred with Lewis and Clark. Can you possibly understand them if you refuse? What if it's customary to allow guests to torture or kill one of the tribe? Can you possibly understand them if you refuse? Some things, I think you will agree, are more important than understanding. In other words, there are moral limits to science, as to law.