Eating chocolate doesn’t make somebody unhealthy any more than a salad makes somebody healthy.
Most people are accustomed to thinking of the food pyramid, but this generally doesn’t help people make adequate dietary decisions. Or they think of “good”/”allowed” foods and “bad”/”banned” foods, and this thinking does more harm than good.
Generally you need a staple in a diet – a food that is easily and cheaply available. Most people choose grains (in the form of bread, cereals, pastas, etc.) as their staple. I choose fruit (predominantly bananas and dates). Some other people choose potatoes or starches, and other people even go with beans. It doesn’t matter so much what staple people choose, so long as they like it, it is high in carbs (obviously, steak is not an acceptable staple!), filling, and relatively healthy (if grains are chosen, whole grains should be sought). Keeping diets simple ensures better success rather than overcomplicating food choices. Then you can add in servings from other food groups (fruits, vegetables, grains, legumes, nuts, seeds, etc.) as you please.
Dr Fuhrman has a good chart and advice based on nutrition density, which lists foods in order of nutritional value. The chart illustrates, in order, that the healthiest foods are raw leafy green vegetables, solid green vegetables, non-starchy vegetables, legumes, fruits, starchy vegetables, whole grains, nuts and seeds, fish, fat-free dairy, wild meats, eggs, red meat, full fat dairy, followed by refined foods as the least healthy. The key is to choose foods highest on the chart and choose lesser amounts of foods towards the bottom. But then calorie density also needs to be taken into account, which is where the staple comes into play (obviously it’s impractical to base a diet solely around raw leafy green vegetables, as you’d never be full!).
In my case, in which bananas are a staple, I could have a banana smoothie with a food even higher in nutrition, such as strawberries. Strawberries are higher in nutrition than bananas, but less filling – it’s hard to have a meal solely of just strawberries.
In the case where grains are a staple, one could have whole wheat pasta mixed with tomato sauce and vegetables. Or maybe for breakfast some whole grain cereal with fruit (coupled with a nut milk like almond milk instead of dairy milk for even greater nutrition and taste). When potatoes or starches are a staple, one simple example for breakfast could be a large serving of hashbrowns. Or for another meal, one of my favourite starchbased dishes: Cauliflower Dal.
A more typical example of an average (unhealthy) meal is steak and fries.
The fries are healthy – so long as they’re not deep fried or cooked heavily with oil. The problem here isn’t even the steak, it’s the serving distribution; the fries should be the main meal, not the steak – the steak should be the side. (A serving of vegetables should also be included, and the serving size of vegetables should be larger than the steak.) Instead of steak and fries, try fries and steak.
If one does desire to include animal products in their diet, it can be acceptable to add small portions of lean meats such as a couple slices of lean chicken breast. Note that chicken is generally high in calories and can easily dominate a meal if not careful; the main source of calories should be the staple food (potatoes, grains, fruit, etc.), or foods higher on the chart.
So, it’s okay to eat a little chocolate, but just keep in mind that it’s low on the chart in terms of nutrients, so there are better foods that could be chosen instead. It’s the overall lifestyle and predominant source of calories which are important, not smaller decisions of greater insignificance such as occasional consumption of chocolate. Diets fail when you start thinking of parting away with much loved foods.