It would appear that the immense pressure imposed by members of the meat and dairy industry has had little effect on the USDA's Food Guide Pyramid. There is no heavy emphasis on meat and dairy products. In fact, other than the "Fats, Oils, and Sweets" category, meats and dairy products are the least heavily emphasized groups in the pyramid. Here's a poorly-drawn representation of the Food Guide Pyramid:


                           /\
                          /  \
                         /    \
                        /      \
                       / Fats,  \
                      /  Oils,   \
                     /   Sweets   \
                    /              \
                   / Use Sparingly  \
                  /                  \
                 /--------------------\
                /          |           \
               /  Milk     | Meat, Fish \
              /  Yogurt    | Eggs, Nuts  \
             /   Cheese    | Poultry, &   \
            /   Dairy      | Dry Beans     \
           /  2-3 Servings | 2-3 Servings   \
          /                |                 \
         /------------------------------------\
        /                   |                  \
       /   Vegetables       |  Fruits           \
      /   3-5 Serv.         |  3-5 Serv.         \
     /                      |                     \
    /-----------------------------------------------
   /                                                \
  /           Bread, Cereal, Rice, & Pasta           \
 /                  6 - 11 Servings                   \
/______________________________________________________\
I think a far better conspiracy theory involving the Food Guide Pyramid is that when it was first introduced during the Bush Administration, people swore that if you looked at is crossed-eyed (like a 3D-Stereogram), you could see a portrait of President Bush. Since the Food Guide Pyramid was distributed widely to public schools, people claimed that Bush was subliminally trying to make kids more comfortable with his image.