Most of the time I don't mind when people believe weird things. What I do mind is when people believe weird things that are counter-scientific — that is, when they fly right in the face of things for which we have plenty of evidence.
The former is things like belief in one or more (or no) gods. The latter is things like the Jenny McCarthy brand of antivaccination know-nothing-ism.
The former is something for polite debate and spirited discussion. The latter deserves to be dragged out into the open and exposed for being downright dangerous.
To wit: the Jenny McCarthy Body Count. I admit the name of the site's not terribly diplomatic (and the sea is also broad, salty, and rather damp). I'm also not sure diplomacy will work anymore, because the anti-vax movement and their associated counter-scientific cronies are not interested in playing nice and are not interested in debating the issues at hand. They are politicians in the bluntest and most cynical sense of the term. They want a captive audience that will help them bring that many more people around to their way of thinking.
Orac over at Respectful Insolence has been pounding on Jenny for a while now, underscoring how the anti-vax crew has no good evidence to support their position (c.f., this recent tidbit). What's become clearer over the last couple of years is how the anti-vax crew could, in the abstract, care less what evidence there really is for their position — it's just that much more fuel for the fire. And unfortunately, many people lap it up because they don't know and don't care that science isn't a popularity contest or a matter of what feels right or a question of who's the underdog (because the underdog is always right).
I am grateful that the public-facing portion of the scientific community is finally realizing that not everyone is going to play nice, and that the other side is far louder, mouthier, and more reckless than they would ever give them credit for. But they need to ramp way up and head off the next wave of counter-scientific lunacy before it gets traction enough to put people at risk.