If I understand you correctly, you're suggesting that bias that leads to wrong conclusions may not be something to worry much about if it doesn't have a negative impact on our life. If so, I guess that could be considered something of a truism on a utilitarian basis, but if our passion is just for truth independent of utility, it obviously still matters. And I'm not sure if we can always correctly measure the impact of mistaken beliefs based on biases either.
I'm very utilitarian about it because I'm not sure that I'll ever be capable of achieving an accurate depiction of objective reality through my limited human capability. Also, after a few months of thinking about it, I'm not sure that my picture of reality has to be accurate. I'm resting my laurels on utilitarianism.
(I'm not even sure I believe in free-will any more but this is an on-going internal struggle. That's another debate altogether. I'm working on a theoretical model for cognition based on the parallels between biology and computation. Hopefully I'll draft something solid and get it academically published. If so, I'll share it here. I'm a non-traditional student studying computer science and neuroscience.)
I think that's not a bad formula for evaluating human behavior and it share some similarity to my own. I wasn't familiar with the term Hanlon's razor, but as a concept I'm a strong believer in it and frequently use it when trying to understand human behavior.
There's another good one to go along with Hanlon's razor! I forget what it is called but (paraphrasing) I think it goes like this: "Malice must be the intention of those who couldn't possibly be THAT incompetent." Human behavior is tough, its the emergence of a complex system of hardware and experience. One thing I have noticed though is that reasoning is always justified for someone, even if it's after the fact. Many bad people in history have justified horrendous actions through the means of necessity and imaginary evil.