That there is a link between the MMR vaccine and Autism has become, unfortunately. and article of faith for some people.
Despite all the studies which show there is no causal link, despite the revelations that Wakefields original study was full of flaws and purpose designed to support a class action against vaccine manufacturers, one thing that has always been problematic is that it is rarely possible to reason people from a position of faith.
Belief in the absence of evidence, in this case done with the best motivations and a sense of guilt.
http://www.babycentre.../mmrseparatelyexpert/