The rationality and intelligence are not precisely same thing. You can pick e.g. those anti vaccination campaigners whom have measured IQ >120, and put them in a room, and call that a very intelligent community, that can discuss a variety of topics besides the vaccines. Then you will get some less insane people whom are interested in safety of vaccines coming in and getting terribly misinformed, which just is not a good thing. You can do that with almost any belief, especially using the internet to be able to get the cases from the pool of a billion or so.