Address why the spread of this unsupported claim is dangerous for society on the whole. Here are a couple of things to consider:
Vaccines save lives and the CDC has put forth a recommended vaccination schedule. There are some who cannot be vaccinated for a variety of reasons. What are those reasons?
Describe why the parents who choose not to vaccinate their children because they are afraid vaccines cause autism are relying on others who do vaccinate to protect their children from vaccine-preventable diseases.
Choose one disease that is preventable with vaccination and is on the rise.
Why is it inaccurate for a parent who chooses not to vaccinate their child to say to a person who will vaccinate their child, "My decision does not affect you if you choose to vaccinate your child."