I have a strong background in science, (Master’s in Physics from Emory University if you’re curious,) not to mention countless hours reading and watching scientific books and tv/online programs. This means that I have been trained to spot weaknesses in arguments, to critically think about evidence presented, and to present and research new ideas.
However, science in no way trains me for how to deal in a non-blunt, non-formal way when presented with ideas in conflict with established science. Suppose you come across someone claiming that a given product is chemical-free . I can go about an argument, (which, in short, would say that yes your product does contain chemical compounds,) in a way which presents the most solid evidence in the most direct fashion, but it can come across as a bit harsh. What good does being right do if the person feels threatened by your method of delivery, or does not understand your terminology , or simply does not want to listen?
By no means am I advocating not educating people or not correcting errors. However, you may have to present your information taking into account your audience. This could mean not referencing x paper or y study, but rather using more colloquial terms and less formal language. The person disagreeing with you likely is not attacking your credibility as a scientist. Use some compassion to figure out the best way to get your ideas across without offending your audience. It may take some time for their established ideas to change. People are not particles.
As for those who are not ready to listen or not ready to learn, there is nothing that can be done until one or both of those conditions change.
For an article which tackles the same topic in a more thoughtful way than my own, please visit the October 2, 2013 post of the fine blog “It’s the Rheo Thing.”
 This appears to be a common bit of advertising for more eco-friendly products. I believe that the intent is that the product which they are trying to sell you is going to not contain, say, strong solvents or chlorine-based compounds. This will very likely be true, depending on the product.
 I am not implying the audience is incompetent, just that they may not be familiar with scientific terms which you use everyday.
[Errata] In this article, I am talking about engaging someone in scientific argument who is not on your thesis committee or at a scientific conference or a peer within the scientific community. In such cases mentioning x paper and y study is highly recommended to back up your arguments. It is advisable to still not be a jerk though.