It's not clear that this is true, though. Psychologically, your average human is likely to assign equal weight to the bad idea and its refutation, which is exactly what you don't want. Moreover, this assumes that people hear both the bad idea and its refutation, as opposed to one or the other from inside whatever cognitive echo chamber they happen to inhabit.

In some cases (climate change denial, flat-earthers, geocentrism, Holocaust denial, etc.), the refutation may also presume a higher level of scientific, historical, or other general knowledge than the bad idea. Bad ideas that play upon our cognitive / perceptual biases have lasted for millenia, and they are very hard to dislodge from the public mind. To some extent, these are all bad ideas that people have to be educated and/or socialized out of.

IMHO, this is one of those precepts that most people want to be true. Unfortunately, we're not yet in that perfectly educated rational utopia :s