[S]imple confirmation bias will ensure that you disproportionately trust things you already believe. And there's nothing you can do about it. Our brains are just wired to work that way.
I don't disagree with the general tenor of your argument, but to this I must object. There's plenty we can do about it: it starts with honestly questioning ourselves as to whether we are letting our biases colour our understanding, and it proceeds by the applying the evidence in attempts to rebut those presumptions ordered thinking demands. Even if few people are motivated to do it, dispassionate fact-checking is possible. While here is no guarantee the conclusions will always be correct (Type I and II errors suck!), we can adopt correct methodologies, which, it is hoped, will draw correct conclusions more often than not and which, most importantly, allow for subsequent correction in light of the evidence (as methodologies built upon poor presumptions may not).
For every complex problem, there is a solution that is simple, neat, and wrong. -- H. L. Mencken