I'm not suggesting only one child in the world is unvaccinated, that would be absurd.

I'm suggesting that if the unvaccinated child never contracts the disease, then there's no harm, right? And if the unvaccinated kid gets it, but doesn't pass it to anybody, no harm no foul again. (To others, that is, which is what we're really discussing as far as first amendment limits right? My fist-throwing rights ends just before your nose)

So what I'm saying is, it's difficult to quantify the expected value of real-life situations because there are so many variables and direct and indirect effects, and because of that difficulty it's easy for many people to ignore relative probability altogether and go with their gut reaction, and that's a mistake, because the relative probability of harm coming from a person choosing not to vaccinate their child is a relatively rare event... and so in light of other very rare events, that we nevertheless do not have much of a problem with (like allowing families with children to have wood fireplaces or trampolines or swimming pools), then maybe, just MAYBE, parents who don't vaccinate are not really that harmful and it's not worth overriding individual choice, even though we all agree that the smart choice is to vaccinate.

Any better?

I'd love you see you quantify the relative probability of all those events with your "math" though, since you say it's so easy. :)