Last year Bill Maher released a movie ridiculing religious beliefs, including those of creationists. But he's now ranting against vaccination (Orac's blog is all over it), saying the same thing that creationists say: The science is not settled, there are many competing theories, so we should have a debate about the facts.
Maher, like creationists, relies on a ridiculous claim about science: Unless we know everything, we know nothing. That's the worst way to distort science today, and it also happens to be the most common: It's the notion that scientists are supposed to commune with absolute Truth. Many times a day, we're told, explicitly or implicitly, that whenever scientists fall short of that standard, their data need not be respected. If there's any debate among researchers, your dental hygienist's brother's cousin's masseur's opinion is just as valid as the experts'.
Those who sell their products or their arguments this way are bad for society. Not necessarily because of a particular opinion on a particular issue, but because they're promoting an unscientific view of science, which encourages people to expect the impossible. Doesn't matter if they're idolizing current knowledge, claiming it's more certain than it really is (which is what genetic testing firms do when they say they can give you precise odds on your risk of getting diabetes). Or if instead they're trying to knock down science by exaggerating the meaning of its debates (see the ``global warming is a hoax'' crowd, and industry front groups who say links between food marketing and obesity aren't proven). The effect on public understanding is the same.
Maybe the reality-based community should stop responding to these people on a case-by-case basis (for instance, by pointing out how safe vaccination is) and instead take on the bigger issue: a model of science that is false at its core.
It's only in fake science that you find a dichotomy between total certainty and total confusion. Real scientists never know everything, but nonetheless know a lot. Their work is not the revelation of eternal truth, but the pursuit of methods for diminishing ignorance (as J. M. Adovasio, Olga Soffer and Jake Page so brilliantly put it in this book). So scientists can't tell you for sure if cheeseburgers will give you cancer or the polar ice caps will melt. But they can tell you what they think the odds are for either disaster, and why they think so, and how confident they are about the prediction. While reminding you that their knowledge and methods are changing as time passes, so the odds you get ten years from now could well be different. Which doesn't mean you can afford to do nothing.
That's not bumper-sticker stuff, but if we don't let scientists treat us like adults, then we're never going to get a handle on global warming, sustainable economics, the relation of disease to lifestyle, or any other problem where multiple causes and effects are intertwined over time.
Whether we like the claims it makes or not, we should all be campaigning against scientific infantilism.