A French Derpy full of Salt

Problem with that is, if anti-vaxers see that vaccination isn't necessary to protect their child, it can encourage them to speak up (and be even more obnoxious) and make them look credible. Since they'd have a logical-sounding argument, more parents would be tempted to skip vaccination, thus effectively erasing herd immunity in the long run.

Which is what I am saying - the best course of action for an anti-vaxxer is to encourage everyone else to vaccinate - that way, they can benefit from herd immunity while not actually vaccinating their kids.

That kinda goes against the anti-vaxxer philosophy though... They have a reason (very legitimate in their eyes) for not vaccinating their children, and since they're convinced of being right, they'll wanna play vigilante.

Not to mention many of them also claim that children must get sick to gain immunity, so they'll want other parents to go anti-vax as well.