Tell him that he has no right to make that choice for others, and while he may think he is only making that choice for his own family he is also choosing to put others at a greater risk. The braking analogy in this article is quite apt.

Prior to the measles vaccine, about 3-4 million people got measles every year. In such a world, a 0.1% mortality rate still leaves 3000-4000 people dead from an easily preventable disease. And this says nothing of the people who suffer from it but don't die. The economic costs from kids and parents getting sick and missing school and work would total in the hundreds of millions of dollars.

Even intelligent people can be narrow-minded. There is much more to a disease than its mortality rate.