No, we don't want to require everybody who sells an orange to pay for lab tests that determine for every vitamin how much is contained. Making such a requirement would be a death sentence for farmers markets.
A customers has certain expecations about what an natural orange happens to be. It's a class of objects that shares basic traits. GMO allows giving the orange traits that oranges generally aren't expected to have.
GMOing is a way of adding nutrients, but we would want additives labeled regardless of how they are added.
Any GMO interventions adds new molecules. If you follow that framework, if you add genes that produce 3 new proteins, put those three proteins on the label.
Basically: How does one pursue the truth when direct engagement with evidence is infeasible?
I came to this question while discussing GMO labeling. In this case I am obviously not in a position to experiment for myself, but furthermore: I do not have the time to build up the bank of background understanding to engage vigorously with the study results themselves. I can look at them with a decent secondary education's understanding of experimental method, genetics, and biology, but that is the extent of it.
In this situation I usually find myself reduced to weighing the proclamations of authorities: