Everything has traces of faeces on it, this fixation on it seems irrational when you put it into context. The burger meat comes from a dead animal that spent it’s life wandering in a field and trampling it’s own shit. The fries come from the root of a plant grown in the dirt. The bun is made from wheat which was probably infested with mice. You yourself are a biological machine that turns food into energy and discards the waste. Your body has a tube filled with faeces right now.
Yes, we try to keep waste separate from food, but the world is not a clean-room.