Peanut butter is one of nature's best protein. Not only is it loaded with protein, but it also has tons of "good" fats. These fats help the body burn fat (fat is burned in a fat furnace) and should be part of anyone's diet.
It is not a bad food at all, even if it is not "natural". Yes, there are sugars added, but by eating the protein and the fat, you stabilize your blood sugar and glucagon levels, which in turn, prevent the body from storing those sugars as fat.