A skeptical principle: appearances and reports can both be misleading, so verify things rather than accepting them at face value. It echoes Shakespeare’s line, “Believe none of what you hear, and only half of what you see.” 😉
People who have very definite views tend to leave very little room for doubt or alternative opinions because they are so certain they are correct. I would say that they can be more dangerous if they want to force their opinions on others.