Yes, it's 100% ideological. I don't want to associate with people who don't believe that vaccines are necessary to prevent illness. They probably have other beliefs that go against science and I don't want those people in my life, or my childrens' lives.

For individuals, vaccines aren’t 100% effective at preventing infection. Primarily, they are useful to increase the herd immunity of large groups, and limit the scope of outbreaks— this only works if enough of the community has been inoculated.

In every measles outbreak, some of the victims are indeed vaccinated. Being unvaccinated based on a whim (as opposed to kids with immune deficiency, on chemo, etc) hurts everyone.