Everyone believes that if everyone else were as informed about a subject as they were, they would reach the same conclusions. It presupposes that other people will put as much credibility on the sources you draw your conclusions from as you do. Being aware of this cognitive bias should make you more humble about your own opinions and your conversations with others about theirs.
Psychologist Lee Ross is interviewed. I note that Ross claims he has "never met someone who met with the other side because he thought he might be wrong or misinformed." In other words, people only meet with the other side to convince others of their own opinion rather than try to weigh evidence against their opinion.
My at least semi-awareness of this bias is one reason I read books by people with different worldviews than my own. I may reject their arguments against my own worldview, but in doing so I know better why that is. I may also be able to find valid points in their arguments that I had not thought of before.