(Note: fast dump - forgive my grammar.
Note: this is not an indictment of GMO labeling nor a dismissal of genuine skepticism re: applied genomics. This is an exploration of themes and frameworks invoked by antiGMO's to describe/convert others to their worldview.)
A few consistent themes emerge when dealing with anti-GMO's:
- Patriarchy: corporatism (and by proxy anything its connected to, ie gene research) is associated as an extension of European Colonialism, specifically WAP (White Anglo Protestants). Rape frameworks are associated solely with WAP/corporate activities - anti GMO's do not level such accusations against indigenous populations.
- Naturalism: In rejecting patriarchy and its associations, WAP actions are categorized as acting upon Nature instead of within it. Nature is seen as a benevolent force that is being interfered with by humans.
- Mysticism: Mystical/magical properties are associated with indigenous people, but only under certain criteria. Native Americans (ie. Hopi) are magical/mystical, but Irish are not.
- Social Privilege: anti-GMO/organic lifestyles are often accompanied by language and images of social privilege:
- "Organic food consumption is one of several new trends in eating read as active opposition to industrialized food provision. While fast food consumption is characterized by compulsive gluttony, manifest in fat bodies, alternative consumption practices are seen to be driven by conscious reflexivity, such that consumers monitor, reflect upon and adapt their personal conduct in light of its perceived consequences." 
- "Namely, the alternative movement has been animated by a set of discourses that
derive from whitened cultural histories, which, in turn, have inflected the spaces of alternative food provision. Many in the movement seem oblivious to the racial character of these discourses – if anything they presume them to be universal – and so are ignorant of the way in which employment of these discourses might constitute another kind of exclusionary practice. Among them I would include the idea of bringing this good food to others. " 
Prop37 proponents will invoke all these themes, but framed as 'choice.' But this is silly - you already know what's GMO vs. heritage. They want a warning label. Full stop.
And they want it because then they have permission to judge you in public: "Oh, you're buying GMO? You must be ignorant." They want to shame you into eating different. Specifically, they want to shame you for contributing to the corporate control (read: WAP) of food and have you embrace a 'natural' way of life. Just like them.
[EDIT: This is a really good article summarizing Prop 37.]
Notes and Citations:
 It is a common assertion among anti-GMO that Native American corn varieties were superior to modern ones for reasons usually attributed to magical properties (ie. 'they lived in harmony.')
 Anti-GMO's will infer the Irish Potato Famine was the result of monoculture choices (this is a punishment framework solely associated with WAP cultures)
 Julie Guthman, Social and Cultural Geography
 Julie Guthman, Bringing Good Food to Others
 Prop 37's #1 funder is certified quack "Dr" Joseph Mercola - this is not about consumer 'choice' or anything real. This man is on a religious crusade to ban all GMO's