Relying on the distinction between knowledge and belief is unfortunately much more difficult than it sounds. To a person approaching a subject in total ignorance, there is no good way to determine truth from well-written falsehoods. People tend to use their emotions as a proxy in the absence of any reliable knowledge.
There are small groups like rationalists who attempt otherwise, but they tend to be found taking modafinil and reading the Sequences instead of trying to convince a worried organic-foodie.
We have many areas in this life where this applies: god/politics/health/climate change/vaccinations/gmo and more. And almost everybody is searching.
Instead of rebutting people, ask them where knowledge comes from, explain them the difference between belief/correctness/reasons. And the difference between opinions based on feelings or based on reasons, and how to spot the differences, e.g. do you know tradeoffs. Ask them how they feel about people with different opinions on the subject.
But people do think. And it might surprise you who will ask you for more information. Worst case you lost a few minutes. Even if they don't change their mind, they do become slightly more "liberal".
Anecdotal, but I have been surprised quite a bit lately ;) the whole trump thing has stirred things up, even here in Europe.
We don't have to make people rationalists or skeptics. But just 10% in that direction would be nice. Perhaps most surprising is how little, or how badly, people have thought about knowledge vs belief.
I think we should all be free to eat whatever the hell we want. I think we should all have food that is maximally labeled with information about all strains of all plants and animals that go into them.
I don't want to force the worried organic foodies to eat GMOs. I want them to return the favor, but they seem hellbent on forcing me to live like them for reasons of fear. That same fear, plus some personal experience, leads me to think they're not really people who can be reasoned with.
That's pretty much the definition of politics. I don't see any future in trying to stop people from doing that.
My first part on trying to answer that is, you acknowledge the human/emotional side of it, and discuss it.
"What you don't get is large masses of people changing their minds." (from your other comment)
No but what does? Propaganda? Silence? Unfortunately both easily used by the "other" side. I think only honesty works and let people figure it out. If ultimately that means we will not proceed on GMO, a shame in my opinion, but so be it.
"I don't think that's actually available"
You might be right, ...
However, I do think there is a second thing we can use. Show people the difference between knowledge and belief. Between opinions based on feelings and opinions based on knowledge. A strong proxy for belief/feelings not knowing or discussing tradeoffs.
"sound just like those people who work for Monsanto - which has happened to me today on HN." (also other comment)
lol, don't we ;) . Luckily the "other" side usually grossly exaggerate their points.
But you are right, ultimately people still have their fears and just grab other fig leaves.