How I see it, LessWrong is a community of people who try to avoid stupidity, including those kinds of stupidity that are very popular among highly intelligent people.

Now the problem is how to write it in a less offensive way. Also, how to write it so that outsiders will not interpret "avoiding stupidity" as "avoiding the people and opinions from the opposite tribe", because this is what most others websites would mean if they would choose such words.

Maybe the problem is that all catchy descriptions are already politicized.

This said, I agree with the proposed introduction. The website description should start with motivation. Only when people are motivated, they will care about what "behavioral economists and cognitive psychologists have discovered in the past four decades", so that part should come afterwards.