The exploitation of other animals for the human diet works to structure a human-supremacist society that is bolstered by dietary speciesism. Since other animals are exploited in large part by humans for diet, dietary speciesism plays a central role in promoting human supremacy in general. That is, as long as we're eating other animals we're benefiting materially and psychologically from their exploitation. As a result of these material and psychological gains we're less likely to challenge the system of human supremacy. Instead, we tend to absorb and perpetuate those socially created ideas that devalue other animals.
If speciesism is the set of socially shared beliefs that legitimize human supremacy, then dietary speciesism is a subset of speciesism concerning socially shared beliefs about diet. Basically, dietary speciesism is the use of diet to promote human supremacy. It is used to legitimize the human-supremacist system of institutional structures, policies, and practices that produces and sustains those dietary privileges that benefit humans and exploit other animals.
One example of the dietary structure of human supremacy is found in the USDA's policies and practices that subsidize and promote flesh, eggs, and milk. That is, through the institutional power of the USDA, the flesh, egg, and milk industries have been able to produce and spread dietary speciesism in the form of powerful (often unexamined) ideas that make the dietary system of human supremacy appear normal and justified.
The dietary system of human supremacy allows individuals to practice dietary speciesism unchecked. As individuals we follow the cultural structure of a basic meal with flesh, eggs, and milk forming the "center piece" or "main course" of a meal. This is particularly true with the forthcoming Thanksgiving holiday in the US, also known as "Turkey Day" for the group of animals that have become not only the focus of the meal, but the focus of the holiday as a whole.
Most of the ways human supremacy is structured into our diet are taken for granted and are simply invisible to us. Even after becoming strict vegetarians, many of us still follow dietary speciesism with a meal structure based on imitating the flesh, eggs, and milk derived from other animals. In these situations we end up subordinate our own vegetarian innovations and culture to the dominant social order. Hence, for a holiday meal we eat a "tofu turkey" instead of celebrating what is in fact roast bean curd and wheat gluten. This is because in our human-supremacist society other animals like turkeys are the main course, while plant-based foods like soy bean and wheat are marginalized.
As vegans we can challenge dietary speciesism and the related system of human supremacy. This includes addressing dietary speciesism and human supremacy on the institutional and cultural levels. On the institutional level we can work to eliminate institutional policies and practices that promote dietary speciesism or otherwise support a diet based on human supremacy. At the same time we can work to institute policies and practices that are based on vegan principles. As an example, the Physicians Committee for Responsible Medicine does some good work related to challenging dietary speciesism and human supremacy on an institutional level, particularly with regard to addressing the policies and practices of the USDA.
One the cultural level we can develop dietary cultural practices based on veganism as well as celebrate dietary innovations without seeking to imitate dietary speciesism or assimilation into the human supremacist structure. That is, we can identify the food we're eating by the actual plant-based ingredients it is made with, as opposed to the flesh, eggs, or milk it's supposedly imitating. On example of this is the Chinese vegetarian restaurant Ever Green House Cafe in Salt Lake City. Instead of referring to what menu items are assumed to be imitating (e.g.,"Sweet and Sour Chicken" or "Beef with Broccoli"), which is too often the case with vegetarian restaurants, Ever Green's menu refers to what the menu items actually are (e.g., "Sweet and Sour Soy Bean" or "Mushroom Stem with Broccoli"). This has the effect of producing and sustaining cultural practices that offer clear dietary alternatives to human supremacy. It also uses visibility and pride to counter the marginalizing effects of dietary speciesism.