Not exactly what you are looking for but a related quote by Charles Bukowski: "The problem with the world is that the intelligent people are full of doubts, while the stupid ones are full of confidence".

Often, on HN and Reddit, the most confident or authoritative sounding statements are also the most wrong. It always baffles me just how confident people can be in themselves when they really have no good basis for that confidence.

I think part of the problem is that we collectively tend to reward the "confident sounding" comments because we wrongly assume that only an actually knowledgeable person would have authored them.