I'd like to think I'm making it based on evidence. Empirically it's pretty clear that, at the very least, the overwhelming majority of children undergo vaccination with no ill effects whatsoever. It's also pretty much empirical that withdrawal of MMR has no impact on autism development rates (eg the Japanese population,
http://www.ncbi.nlm.nih.gov/pubmed/15877763 , which study even reports autism rates
increasing on withdrawal of MMR, although that link is unlikely to be causal).
Measles is, incidentally, potentially fatal. In the UK, the danger is fairly slight, but in other countries the death rate is not insignificant. It's much lower now than in the past, but in 2013 nearly 100,000 people died from measles or related complications. So MMR matters, and the world is a somewhat healthier place for its existence.