The worst thing about the vaccination "debate" (that, by the way, is certainly not "great") is how it stigmatizes autism in a backwards way.
Even if it did cause or contribute to the development of autism, how is autism so bad that it's worse than your child dying of an easily preventable disease? How is it worse than your child potentially becoming the source that spreads an easily preventable disease to other people who then become terribly ill and possibly die? If your child did develop autism, how would you feel if they knew you'd rather they potentially died of an illness most people are immune to? I doubt that they intended that message, of course, but what is so awful about having a living child who is autistic that you'd choose the risks of the alternative?
Just.. ugh.
That's the thing; some of what we vaccinate against is really significantly worse than autism. Would these folks rather that their kids develop polio? I would hope not.
I think most of them are somehow convinced that it's a scam and that these vaccines don't work anyway, and/or that autism is just the tip of the iceberg in terms of health problems from them.