To me it is just as silly to say that you will eat meat and absolutely no plant products as it is to say you will eat plant products but absolutely no meat. (I am not referring to arguments of conscience or religion, that is a whole seperate topic.)
Whether you believe that we were sculpted from clay to be exactly as we are or that we evolved over millions of years, recognition must be made that however we got to be how we are, we were designed to eat both plant and meat products.
Every one of us has a natural reaction to most types of food. The smell of beef being grilled is almost universally appealing, as is the scent of citrus fruit. Most people enjoy the flavor of bacon and even if they don't eat the real deal do sometimes have bacon "flavored" foods. I realize I am making generalizations here, but my point is that if our minds and bodies instinctively respond to a food, then we were meant (or evolved) to eat it... in some quantity.
For example, our teeth are a good clue. Sharks eat nothing but meat, and they have nothing but razor sharp teeth for shredding muscle tissue. Deer do not eat meat, and their teeth are flat for grinding plant matter into pulp. Humans (and other omnivores like dogs and cats) have a blend of these types of teeth. We have sharper teeth to cut through and shred meat but also flatter teeth to help us grind away at plant foods.
Another example is our ancestors. They hunted -and- they gathered. They ate what was available and what their bodies told them was proper... based on the natural order of things.
My last example is about how certain foods are simply not appealing alone yet we eat cubic tons of them. Vegetable oil is in most processed foods if there is a fat content, it comprises a good bit of what margarine and mayonnaise are, and then there is deep frying. But if you take a bottle of the stuff (vegetable oil is usually corn oil) and smell it or taste it, it's pretty nasty. The one exception in my book is olive oil... preferably extra virgin (cold pressed is the kind which is easiest to extract and doesn't require heating). I can dip a piece of bread in olive oil and eat it and that is just about as pleasing as putting butter on bread. I can't say that about the types of oils that are normally used in mass production foods. Butter - an animal product - is what oils were trying to replace in our eating habits. Butter makes better cookies and breads, fries things to a lovely golden brown, and it tastes amazing simply spread on toast. But because it is an animal product it's considered taboo. Though butter is extremely rich, and I wouldn't eat a quantity of it alone, it's not because it is unappealing only because it is too much fat with nothing to balance it. If I get some on my fingers, I happily lick it off. If I get some oil on my fingers, I look for a paper towel to wipe it off with.
And as for a side note...
Neither humans nor animals were intended to eat so much grain. Not only do we consume tons of wheat and corn, but we also only eat meat which has been fed tons of wheat and corn. Corn as we know it does not occur naturally. Natural foods are ones which do not require any advanced farming to grow - no cross breeding or selective breeding to get what you want, but rather eating what you find. Most completely natural maize is inedible... it was bred to be what we eat today.