Prof. Noam Chomsky should have been let into the West Bank. Yes, he's a harsh critic of Israel and yes, he has met with terrorists such as Hizbullah head Hassan Nassrallah, but he isn't a terrorist himself. During his visit to Birzeit University, there's no chance he'd do anything to aid Hamas, Islamic Jihad or any other violent group.
My main objection to Chomsky's denial of entry is on the grounds of freedom of speech, but those who don't care about silly things like rights should think about this: Not allowing someone into the Palestinian territories only because of the criticism of Israel he'd voice while there is ridiculous, since many of the locals say much worse things about Israel than he does. Not allowing a person into Israel proper (which wasn't the case with Chomsky, who was planning on visiting the West Bank only) is equally as dumb, since we have so many left wing professors saying terrible things about Israel at Israeli universities every day. Another reason that this is dumb is that a person denied entry like this usually gets more attention than a person who goes in.
Sometimes, denying someone entry is alright. Norman Finkelstein, who is much more extreme than Chomsky and seems committed to the destruction of Israel, was barred from entering Israel a few months ago and I think that in that case it was the correct decision. He's quite the rabble-rouser who could have actually incited Palestinians to act violently against Israel (and he's not against violence). Noam Chomsky ain't no rabble-rouser, and probably neither is the Spanish clown, Ivan Prado, who was denied entry at Ben-Gurion Airport last week.