It's rational for them to lobby against GMO labeling because it's a lose-lose proposition, even if they honestly believe their food is safe and eat it themselves. Either it scares off consumers (some of whom won't know what GMO means but understandably assume it's bad because it's disclosed) or they have to spend a bunch of money on "consumer education" and lose some of them anyway.
That's whether GMOs are safe or not.
Water companies would also lobby against "Warning: heavy water" and Cisco would lobby against "gigahertz radiation" labels, but not because they have something to hide.
But without a label of the form "contains GM ingredients", I am being deprived of choice about what I eat. It's reasonable to expect people to care a lot about what they eat.
> Water companies would also lobby against "heavy water" labels
If you mean labelling ordinary water as "heavy" because it contains a tiny amount of deuterium, I'm not that's analogous. Even if it is, I'm not sure that saying "They would say that, wouldn't they" makes their arguments against labelling more persuasive.
It's not a prefect analogy because it only really captures the producer's point of view. They are hiding the product's heaviness or GMOness itself, but because they think that doesn't tell you anything about its safety or general worthiness and so should not be part of your decision.
You should still be able to avoid the product for environmental reasons, or just because, but of course they don't think so. (HN's favorite Sinclair quote about men and salaries and understanding.)
A heavy water molecule has deuterium in place of hydrogen; the extra neurons make it "heavy." Most water has some miniscule amount of heavy water in it.
That's whether GMOs are safe or not.
Water companies would also lobby against "Warning: heavy water" and Cisco would lobby against "gigahertz radiation" labels, but not because they have something to hide.