Publicly refuting facts often reinforces their believed truth in the minds of the public, and they will even credit the misinformation to the organisation denying it.
A Washington Post article reports an experiment where people were given fliers labelling common ideas about influenza ‘true’ or ‘false’. Half an hour later older people already remembered 28% of falsities as facts, and three days later 40% , by which time younger people caught up to the older people’s half hour figure. It seems that the repetition of the false information helps to ingrain it, while the extra information – that it is false – is soon lost.
So how do you have factual public debate when whoever starts it automaticly has a major advantage? Denial and silence can have the same effect as agreeing, but denying is still best. A good proportion of people (a few days later at least) do remember whether their facts are false or not. Though as TWP discusses, it’s probably best to deny things without actually mentioning them if possible. That is, fiercly support something mutually exclusive.
As noted in the discussion of Overcoming Bias’ post on this, if people have anything at stake they might pay more attention. While this has problems of its own (discussed there), a big obvious gap where it’s important for people to have accurate information on topics not directly concerning them is in democracy. Just another in a long list of problems with the kinds of democratic systems we use, but in conjunction with rational ignorance it makes the chance of voters having a clue about anything not immediately concerning them both tiny and tied firmly to the chance of the first buyer of lots of ads happening to be right.