What's the problem with labeling GMOs? Let me try this.
Some crops are watered only by rain (we call this dry land). Others, have irrigation systems (we call this irrigated land). This is a decision a farmer makes, based on his location, costs, climate, risk and other factors. The end result of the crop is the same in terms of safety and nutrition. You cannot tell the difference between a kernel of corn from dry land or irrigated land.
If someone were allowed to create a label that said "Only naturally watered" in reference to dry land, that would be implying this is a better, or safer production method. (It's not.)
The result for consumers? People respond by either paying more for a label that means nothing, or they discount or avoid products without the label (which means nothing). People are not MORE informed. They are actually LESS informed. They have more information sure, but the information is not valuable information to making a good choice.
The result to farmers? They would potentially have to alter production practices in order to meet some marketing created demand from consumers. Families that live in areas that cannot produce a crop with irrigation? They go out of business. Overall yields go down, acres suitable for production goes down, the number of farmers goes down.
There is no difference on a GMO label. It gives you information sure, but it tells you NOTHING.