Wouldn't you be upset if your in-laws served you seitan that was actually chicken?
*edit: I bring this up because many people do not react well to meat substitutes. Gluten and soy intolerance affects many people and serving soy or gluten-based meat substitutes without prior informed consent can induce adverse reactions. I do believe that veganism in morally superior to carnivorism, but that still doesn't grant the right to trick others into consuming meat substitutes without their informed consent.