It really depends on whether you believe the vegetarians or the bodybuilders.
Most people need more protein than they currently get, but it depends on various factors (size, muscles mass, etcetera). Although protein is key for many functions and has a huge impact on fat loss, muscle building and detoxification, too much protein from animal sources can also be taxing on the digestive system and cause an undesirable increase in pH.
Different people thrive on different amounts and of macronutrients (protein, carbohydrate and fat). We all need all of these, but in different ratios. Many people's diets are too high in the wrong type of carbohydrates (bread, pasta, rice, etc) and this leads to weight gain. Some people on a higher proportion of these carbohydrates in their diets, the majority of us however do not and should therefore be eating a higher proportion of protein and fats.
In bodybuilding circles, and in an increasing number of fat loss approaches, many people advocate huge amounts of animal protein, with greens, zero fruits and no other forms of carbohydrate. Spot on if all you care about is getting lean very quickly. Not perhaps so good for your digestive system and general mood!
Conversely, vegetarians taking in no animal protein, in our opinion are missing out on many essential amino acids, fats and nutrients, which are key to overall health. Not to mention that protein consumption plays a big role in liver detoxification, building muscle, increasing strength and shifting body fat.
Our approach is probably somewhere in the middle. Even from a sports performance perspective, we have found that it is possible to consume less animal protein and still maintain muscle mass and strength levels - although pre, during and post workout nutrition has to be spot on. No matter, you must eat plentiful vegetables.
The bottom line, is that you need to eat according to your requirements and these vary hugely from person to person. It's worth remembering also that quality is as, if not more important, than the quantity.