As in all things nutritional, you can have both excess and deficiency. Your body needs protein and beef and pork are both excellent sources of complete protein. However, too much meat, especially red meat, can contribute to obesity, vascular disease and cancer. If undercooked, meat can also carry diseases (as can vegetables if not washed properly). You can get the needed protein from other sources such as leaner meats (like chicken and turkey) and fish and also from vegetarian sources.
Nearly all non-meat and fish sources are incomplete and so care must be taken to use complimentary sources (just eating salad is not healthy). Vegetables, lentils and legumes are higher in vitamins and fiber and lower in fats, however, they are also low in bioavailable iron (the iron in green leafy vegetables in not easily absorbed) so care must also be taken to address this need.