WS: I do not know who paints such an image, except perhaps some right wing talk show hosts grasping for straw men.
As Pierre Bourdieu showed in _Homo Academicus_ - the academe is as divided along political lines as the rest of society. That division coincides with disciplinary boundaries: there are left wing disciplines (sociology, anthropology) and right wing disciplines (economics, law, management). Those disciplines attract people with respective political orientation, and also serve as the pools of cadres for political and economic institutions (corporations, government).
This system works regardless of the actual political orientation of individual people. If you claim having a degree in, say, sociology, on your job resume, you can be almost certain that you will get a flat rejection notice from most corporations. Job hunting specialist would advise you in such a situation to omit the field in which you have your degree (give only the degree you have, say, PhD, Rutgers University) and instead focus on your skills, and say for example that you are a statistician (if you can crunch numbers) or pollster (if you know how to do survey research), etc.
Therefore, no one with actual decision making authority (especially about hiring and recruitment) complains about "liberal bias" in the academia, because they know how the system works and where to look for the appropriate candidate need for a particular position. The only ones that complain are right wing ideologues - they do so only because conservatism is a mental disorder and their brains need a scapegoat to function.
Wojtek