Remember, nobody is going to change their mind on this issue because of a perfectly worded response in an internet discussion. If you want to change anyone's mind, focus on the people you can speak to in the real world—and have a conversation filled with love and respect. Trust in vaccination is a powerful meme which cannot be countered by deriding the people who are sincerely captured by it. Instead, I suggest you walk them through the statistics and place them into human terms and human context. Show them how to calculate risk of death. Show them how to calculate risk of long term injury.