Well, you probably bother because you care, and caring isn't a bad thing at all.
I know two people to whom I can talk about the food supply. Most others just know I don't eat corn chips. One is someone who has an old friend who put her MS into remission following what he calls "the caveman diet," and the other is a cook who, while not opposed to grains and legumes, doesn't hesitate to pay $5/dozen for eggs from the farmers' market, and just loves to talk food. I don't really approach it as a way of life, just as an old hippie who is disgusted at the garbage being sold as food.
People are interested (sometimes) if you approach from "there's pus in the milk suppy because," "soy gives you man boobs because," and "girls menstruate two years earlier than they did 50 years ago," because that doesn't really put them on one side and you on the other. Those are things that are a concern to almost everyone.
"Right is right, even if no one is doing it; wrong is wrong, even if everyone is doing it." - St. Augustine