Perhaps you did not pick the correct biases? Remember the way that Rational!Harry convinced Draco Malfoy? You need to start small. First produce a belief that your methods lead to more correct results, then build up more and more biases and have them create a more accurate picture of the world. Then when you have a critical mass, go for a bias that is more central to their worldview. You need your ideas to be strong enough to win the inevitable contradiction war.
Consider that LessWrong is a self selected community. People come here, read the site, and only stay if they agree. What if out of 10000 potential members the site only convinces 5% or 10%? And furthermore the people who disagree here don't have the power to control the conversation so as to throw off people on the fence or people who have a small initial agreement.
Personally my anecdotal experience, re: convincing people of atheism, is that you need to focus on doubters and even then you maybe only get a 1/10 ideal result. Group conversions are unlikely to be effective. Maybe aim for a few people to talk to you afterwards about more info on the topic.
I'm afraid I haven't properly designed the Muggles Studies course I introduced at my local Harry Potter fan club. Last Sunday we finally had our second class (after wasted months of insistence and delays), and I introduced some very basic descriptions of common biases, while of course emphasizing the need to detect them in ourselves before trying to detect them in other people. At some point, which I didn't completely notice, the discussion changed from an explanation of the attribution bias into a series of multicultural examples in favor of moral relativity. I honestly don't know how that happened, but as more and more attendants voiced their comments, I started to fear someone would irreversibly damage the lessons I was trying to teach. They basically stopped short of calling the scientific method a cultural construct, at which point I'm sure I would have snapped. I don't know what to make of this. Some part of me tries to encourage me and make me put more effort into showing these people the need for more reductionism in their worldview, but another part of me just wants to give them up as hopeless postmodernists. What should I do?