I can agree that I'd rather have real food, ingredients raised by farmers, than artificial flavors in my food. Also, she's right, America needs to exercise more. There are things we can agree on. As a kid, artificial colors made me hyper. Jello would make me bounce off the walls. However, food based dyes are expensive and drive up food cost. 
There are things we can find common ground on. She likes expensive organic food. There are farmers that are happy to meet her needs.  There will still be demand for cheaper, non-organic, cheerios and frosted flakes too. ON the other hand, saying my GMOs  are poison is unfounded and pisses me off.