The emotional and reactive sharing of misinformation is shared even when people are open about their uncertainty about the source ("I don't know if this is true but it makes me so mad!!") Judging by behaviors over the last decade, people aren't going to stop and fact-check every article they scroll by, even when sources like Snopes and Politifact are widely known. My conclusion is that change hinges on treating the sharing of misinformation as dangerous; not "I'll share this in case it's true" but "I can't share this in case it isn't."
From a public library perspective, we should be engaging with our patrons online. Maybe we encourage people to tag their local library when they see an article they aren't sure of - maybe we offer a weekly roundup of the top 5 most misleading stories and why they're so effective - maybe we offer more ways to connect with their neighbors where people can see that the Other Side aren't all a bunch of [political bogeyman]ists. Surely there's a lot more we could be doing that is more likely to reach a lay person than classes on media literacy. (Not to be dismissive! But they only reach a fraction of the people who need it.)