If we don't close the Gitmo Detention Center, we let the terrorists win.
Either it happens through us handing the real terrorists an awesome recruiting tool, showing the world how we imprison people (suspected terrorist or not) and hold them without a trial and torture them, or we destroy our own principles and beliefs in pursuit of fighting terrorism. We stare into the abyss long enough, and it stares right back. Terrorists can knock down buildings, they can kill, but only we can take our freedom and rights away.
Gitmo was a cluster**** from the beginning. I'm not even sure how many people being held there are actually connected to any terrorist organization. When we went into Afghanistan, we offered rewards to the Afghans for them turning over people they suspected were connected to terrorism. Of course, they never gave us any proof when they gave us these names, so they very well could have been turning over the village idiots or people they didn't like. Powell's chief of staff just recently came out and said that Rumsfeld, Cheney, et al. knew that innocent people were being held in Gitmo, but refused to release them, because it would make us look bad going into Iraq.
We're Americans, we either believe in human rights for all, or for none. Torture is evil, and I have no idea why the people who authorized it aren't on trial for it.