All of us have biases; that's something that's part of how the human brain works and simply cannot be avoided. The approach taken on LessWrong is not to purge oneself of biases, but to identify these biases and then consciously attempt to work around them in some way. It is implicit in this mindset that one will always have biases whose existence may not even be known. As long as everyone agrees with this, I don't think the community would devolve to that level.

The person who wrote this article has taken the first step - she's admitted to having a lot of biases that prevent her from accepting arguments that oppose her viewpoints. I'd like to see her take the next.

I'm not sure I understand your comment, is the "they themselves" referring to people in the 'rational' community or outside it?

Furthermore, in-groups want to co-opt any 'rationality' movement as their own, so that they have more soldiers to attack opposing viewpoints -- to wit, labeling it as disagreement with the 'rational' point of view. See rationalwiki for a horrific example of this.