A family friend had a huge overreaction to a potato salad. If someone is kind enough to invite you to their house for a meal, you often bring some nice drinks or a plate of brownies or a bouquet of flowers. What you don't do is insult the food that your hosts have made for you — no matter how much you dislike it. Most of us are taught that as toddlers. We're told, "If someone gives you a birthday present, and you don't like it, what do you do?" And then you learn to say "Thank you!" for what yo…