I'd feel proud if my car only burned dead dinosaurs, but I guess that it's mostly different species (and plants) that have been dead for a while and now are in its tank.
Gelatin (as well as other weird stuff) is surely included in some yoghurt products, but not in pure (original) real yoghurt, which should only contain milk and bacteria cultures.
I never felt guilty for eating (or using products that are made of) animal products.
I feel that unnecessary harm to animals is unethical (like experimenting on them for products that are not essential to humanity, like cosmetics), on the other hand.