think of genetic modification as a tool... it is used to alter one set of genes - usually by adding a "new" characteristic.

Think of rice... a major food for billions of people. Add the gene to produce Vitamin A in rice , golden rice, and millions of people are no longer at risk of that vitamin deficiency.

Taht same tool can and is used to make crops resistent to pesticides that are then applied to the crop at high rate that kill off other unintended species.

A tool like cosmetic surgery can repair a cleft palate... or just make someone look different. A tool... it's how that tool is used that is important.