If you want to start an argument on Facebook, just bring up vaccinations. To me, I feel like arguing about whether or not your child should get them is kind of ridiculous. I, personally, don't know a single doctor who's against vaccinations. And the overwhelming majority of the world's physicians are all about them. So you'd think that'd end the debate.
But no, there's always someone, somewhere, who's willing to dig up some link to a doctor with a questionable past or reference a single medical journal that somehow disputes all the other scientific literature, statistics, and other studies that disprove vaccinations cause autism or are otherwise harmful.
But if you need any further proof, just look at what happened to this small community of primarily Somali-Americans who were convinced by an anti-vaxxing group that vaccinations were harmful.