Liberal intelligence is the extremely limited set of criteria which liberals use to define "intelligence." In so doing, they ignore the reality shown by modern psychological research: intelligence is a multi-faceted phenomenon which is not easily measured, and the assessment tools which liberals prize so highly are severely flawed.
Liberals frequently attempt to equate liberalism with intelligence, citing studies which show a correlation between liberalism and I.Q. This connection is observed even by liberal professors; George Washington University professor James Bailey acknowledged the link between elitism and liberalism, saying that liberalism and atheism may be embraced by some as an attempt "...to communicate to everyone that you're pretty smart."
It should be noted that liberals who engage in such behavior are hardly the first to attempt to use IQ tests as a means of declaring one group superior to another. Indeed, the pioneer of psychometrics, Darwinist Francis Galton, believed firmly that white members of the upper class were intellectually superior to those who were not part of this elite group--namely, members of other races and social classes.  Not surprisingly, given that Galton was also one of the fathers of the eugenics movement, eugenicists seized on I.Q. as a means of justifying their doctrine.
Thus, intelligence of the sort that liberals value has commonly been used as a means of justifying segregation--segregation between the intellectual elite and the common masses they disdain, segregation between races, and (in the case of the eugenecists) segregation between those who are judged "fit to live and reproduce" and those who are deemed unworthy of these privileges.
Setting aside the severely questionable historical roots of their position, those who idolize liberal intelligence are also overlooking decades of psychological research. Over the last 25 years, Howard Gardener's research into multiple intelligences has called the value of traditional IQ tests into serious question. Indeed, Gardener's model of multiple intelligences is accepted by the mainstream psychological community as being a much more accurate depiction of human cognition than traditional IQ tests, which heavily favor linguistic intelligence (an area in which liberals tend to excel.)
The ultimate failing of the liberal intelligence model is that it fails to take into account the many areas of intelligence in which liberals do not excel. A liberal professor with lackluster linguistic intelligence may sneer at a "lowly" auto mechanic, despite the fact that the auto mechanic exhibits great mechanical intelligence. Likewise, liberals frequently denigrate the concepts of insight and wisdom, since these are aptitudes which are beyond the control of the intelligentsia.