On one hand I agree with you, the way “chemicals” are used in everyday speech differs from the text book definition.

On the other hand, if we take our heads out of our asses and stop the "well actually"s I kinda have to agree with being against “chemicals” in food. Arsenic is naturally occurring, sure, but at what concentration? Radioactive uranium is a naturally occurring element, but I would hardly call nuclear fallout something natural.