Naysayers are people or critics who are against your opinion or your ideas and they are right a little bit. and they have evidence to back them up. It's important because it is a "They said" and you want to proof them wrong. For example a naysayers would says a honda car is better than a toyota, because of it's Interior features. I would say a honda car might have more features but it is not the better car even though both cars are almost the same, toyota saves more gas.