It is said that Gm food is bad because it leaves things behind in us, possibly causing long term problems. Food allergies also has sky rocketed with modified food. There has also been a higher rise in Autism,, reproductive disorders, digestive problems, and others on the rise. Gm contaminate. Most Gm crops are engineered to be herbicide tolerant, meaning they are designed to survive weed killers.And finally, the herbicides that the Gm is able to survive, sadly it kills birds, marine life, insects, and soil organisms.
Hope this helps.