They are highly educated and intelligent. Of course they are liberal. I wouldn't say they necessarily have a bias though. I said yes simply because I agree with the notion but I disagree with the wording. As a liberal I have a bias, we all do. That's just the way it is. Business folk have a conservative bias. Smart folk have a liberal one.
I studied business in undergrad at a Jesuit school and also had a good chunk of liberal arts classes mixed in. There is definitely a bias at most universities. I don't think this is up for debate, I think this is pretty much a fact.
The better question is why it is so? I am not sure but in general, the educational profession is supported by liberal policy. It is also a self fulfilling prophecy. Liberals teach at schools and to become a professor you need years of graduate education.... So you have more liberal influence. AND the circle goes round.
@imfairlyliberal - i am guessing you are also fairly young. Being liberal is not evidence of intelligence. Both parties really have an equal split of college graduates and I would argue liberals own the least educated - or those without a HS diploma. As you get older you will see a lot of your "smart" friends ditch the democratics. Winston Churchill said it best "If you're not a liberal at twenty you have no heart, if you're not a conservative at forty you have no brain".