Yes, there are some legitimate problems with GMOs, but they are legal issues, not health or environmental ones, and no one is talking about the alternative: More fertilizer, more water, more land use, more fuel to get less food.
Regardless of this, why shouldn't food be labeled with that it is?
If you want to buy genetically modified products since they're less environmentally straining, or for other reasons like higher nutrient values or such, you must have labels to be able to make this choice.
If want to stay away from genetically modified products due to being afraid of potential harm, or other reasons, you must also have labels to be able to make this choice.
What your choice or reasons are is irrelevant to the question of labeling food. Without relevant labeling, you have no freedom to choose what you eat.