It comes from a Skeptic Facebook page called Refutations to Anti-Vaccine Memes. I've noticed this used even when the topic at hand is not vaccines, as it seems to be used to discredit these sites with the argument that they are just trying to sell you something. I definitely think it's fair to be skeptical of that, and each one of these websites used as examples would need their own discussion to ascertain whether or not the information found there is generally reliable, of course.
I think it's interesting that they are making the assertion that 'pro-science' sites are 'just trying to give you the truth.' Since so many Skeptics claim to be pro-science, evidence based and refer to themselves as 'science communicators', I decided to apply the same reasoning to their own websites.
Lo, and behold - look what I found!
The question I am left with is why is it okay for them to have a store, and for them to sell things, but not okay for others? That feels fairly hypocritical.
This is not to say, that I think selling something automatically discredits someone. I do think you need to base it on more than that, and the argument - look for the store! - is not a very effective one.
Some fallacies that apply here:
Bias Blind Spot – the tendency to see oneself as less biased than other people, or to be able to identify more cognitive biases and faults in others than in oneself."Pro-science ones are just trying to give you the truth."
Ingroup Bias Projection – when citing superior morality, rationality or intellect as traits more likely characteristic of members of one’s own group.
Ingroup Bias – the tendency for people to give preferential treatment to others, or the ideas of others they perceive to be members of their own groups.
Giving preferential treatment in this instance by using the existence of a store or product to discredit someone, while not applying it to your own group. The implication that it's okay for Skeptic websites to have stores, but not okay for ---> these people.
Inverse Argument from Authority – because it says something in Breitbart, Fox News, ad absurdum, therefore it follows that it’s false. Inverse of Argument from Authority, possessing the same flaw.
Using the meme to discredit an entire idea proposed as false because the website has a store - instead of addressing the idea itself.
"When in doubt just look for: The Store™"
In conclusion, while it's always a good idea to be skeptical of anyone trying to sell you something, it's important to apply that skepticism equally. That includes questioning those who claim to be pro-science, since they are just as likely to be selling something as anyone else. One can buy, sell, or receive compensation for what they do in many forms - it's not always just about money. Having a store - or not - isn't the best way to determine if a source is credible.