Manufacturers and politicians defend GE foods on the basis of safety studies (results of which are still far from conclusive). However, there are reasons other than safety that consumers cite for choosing what to eat, e.g. ethics, religion, dietary restrictions, international trade and fair trade (Europe doesn't want our GE grain or livestock). Labeling places power back into the hands of the consumer.
Withholding information about GE foods treats the consumer with contempt ... "We know what's best for you." I respect that there are people in industry, in government, and in other decision-making positions who are comfortable with GMOs. I wish they would respect my need as a consumer to be informed, so I may choose to be comfortable with them too ... or not.
When GE foods were labeled in Europe, manufacturers sought non-GE ingredients. Demand for GE foods decreased, acreage planted decreased.
We need labels.