Probably none of us is totally non-gullible. As individuals we vary in the degree of our gullibility.
We believe what we want to believe. Unfortunately most people’s beliefs are products of negative emotions such as fear, hate, greed, vanity, and self-righteousness. These vices enslave us, and yet we call ourselves “rational.”
All gullibility begins with lies we tell ourselves. And the lies we tell ourselves are products of negative emotions.
Put another way, all failures of intellect begin with failures of moral character. Since no one but you can improve your moral character, no one but you can awaken you from the lies that you defend. Facts, logic, and evidence are useless. You twist them, filter them, and interpret them in a manner that justifies your personal character. We all do this.
With the people below, for example, nothing can penetrate their delusions, since nothing can force them to drop their personal hatreds. Only they can do it.
Until they do it, they remain ugly, violent, and stupid.