thought I'd just jump in here and state that Dr Fuhrman does recommend fats/oils within his plant-based nutrient-dense diet in the form of a tablespoon of flaxseed oils daily, including nuts and avocados, where the latter contains monounsaturated heart-healthy fats.
Flaxseeds and their oils provide (amongst other valuable nutrients)) Alpha Linolenic Acid which is converted into DHA by the body, but in insufficient amounts for the bodys needs: hence he believes in supplementing with plant-derived DHA or a fish oil equivalent, if you are not vegan or vegetarian.
Plant-derived DHA (docosahexaenoic acid) is a little more expensive than the fish-derived DHA.
Some fats/oils are essential for health which is why some of them are referred to as "essential", as they are only available from outside sources and not manufactured within the body.