I enjoyed this pair of comments on a post about anti-vaccine crackpots on the Gin and Tacos Facebook page.
It's neither worth it nor interesting at this point to address the basic flaws in anti-vax arguments. However, I think this comment illustrates why so many of these half-assed pseudoscientific theories are finding receptive audiences these days: it seems like it makes sense. To someone without a basic understanding of anything scientific or medical – that is, about 95% of American adults – it makes perfect sense that exposing an infant to many different diseases at once would "overwhelm" them. It's not correct, but a semi-reasonable person without any real understanding of how vaccines or the immune system work could read this and think it sounds perfectly reasonable.
If you're one of the increasing number of people for whom "Sounds about right!" is a suitable replacement for accurate information – and so much easier! – the scientific facts gleaned from Tumblr leads down some very strange roads.