Both denial of rigor and denial of objective truth are functions of neoconservatism as manifests in the Tea Party movement and in objectivism. One has no further to look than a brief watch of Fox News or any of the other conservative news outlets to see it in practice.
The liberal bias which intelligence takes is that it prefers on the side of flexible humanism rather than the dogmatic, theocratic reality of conservatism in any form.
This bias manifests as concern for the present and future - both of which can be manipulated and remain transmogrifiable - than for pining for an imagined and concrete past to the point of rewriting it to fit one's paradigm.
It manifests as fascination with the truth that only science can provide rather than the veneration of creationist myths.
Liberal bias means searching for the truth in whether it's better to be materially wealthy or fraternally rich.