Charlie Reese—who is in my mind not exactly a bastion of liberal thought— explains why in this article. One of the better points he makes is this one:
If Muslims really desired to conquer the world, don’t you think it’s strange that we’ve been living in peace with them for nearly a millennium and a half, except for those times when we attacked them (the Crusades, the European colonial movement and our invasion of Iraq)? Don’t forget either that some of the countries the Bush administration calls allies are themselves Muslim – Egypt, Jordan, Kuwait, Saudi Arabia, etc.
The moral of the story is simple: if you’re afraid that if we pulled out of Iraq, the Arab hordes would swim to our shores and knife us in our sleep, relax, it’s not going to happen. What you should worry about more is the fact that our government is presenting that idea as a foregone conclusion–which it cannot be since it hasn’t happened.
Being prepared and willing to defend our soil is one thing. Swallowing government propoganda is another. The first can be defended on principle, but not the second.
At the very least, the article is worth the five minutes it takes to read. Enjoy!