I actually disagree; the "Rationality" tagline is highly appropriate, especially as the singularitarians here are devoted to rational thought processes anyway in AI research.

I would, however, like to point out that the site seems to get mixed up with other groups as well:

"RationalWiki" - the highly politically partisan pro-science web page (kind of an opponent to LW, apparently.

Rationalism (philosophy) - Spinoza, Leibniz, Descartes (but they pretty much ignored empiricism so they have little to do with LW thinking)

Rationalism (Ayn Rand) - the worst kind. LW isn't a social-engineering organization, especially one committed to absolute "rational" selfishness.

So the tagline is good, but we should try not to get mixed up with those groups.