Also at the Plank, Jonathan Chait says that Joe Lieberman is wrong:
Yes, most American liberals devote more energy to opposing domestic conservatism than to opposing foreign totalitarianism, even though the latter is vastly worse. Lieberman’s mistake is in assuming that this is because liberals think Bush is worse than bin Laden. In fact, it’s because our society aggrees that Islamist extremism is evil, but it doesn’t agree that the Bush administration is very bad, so we spend most of our time debating the point of contention.
One could make another defense of liberalism here: that liberal denunciations of our government’s policies are more likely to change that policy than liberal denunciations of our enemies will change their behavior.