Anti-vaxxers. I had to seriously bite my tongue to keep from going off on a friend-of-a-friend on Facebook tonight. Our mutual friend posted a link about the latest measles epidemic with a reminder to vaccinate kids, and the friend-of-a-friend started ranting (in mostly all caps, naturally) about government propaganda and autism and how vaccines poison our children and blah blah. Holy crap, that nonsense boils my blood instantly.
I put a lot of the blame on the media which tells people that there are two valid sides to any story even when -- as a completely hypothetical example -- one side is scientific, peer-reviewed fact and the other side is horseshit nonsense that has been debunked time and time again and shown to be largely the fiction of one man whose falsified "studies" were created to profit himself directly.