In 1993, a terrorist plot to destroy the World Trade Center towers in New York City did not succeed in toppling the towers, but the 1,500lb bomb killed 6 and injured over a thousand.  5 men were eventually convicted of carrying out the attack.  All of them are being held in prison here in the United States.

A sixth man, Ramzi Yousef, the mastermind of the 1993 attack, went on to plant a bomb on an airliner.  He then plotted to explode 11 passenger airliners over the Pacific, but was caught shortly before it was to happen, so his most massive terrorist plot was foiled.  Where's Ramzi Yousef now?  In prison in Colorado.

That same year, a terrorist bombing of the Murrah Federal Building in Oklahoma City killed 168 people.  Timothy McVeigh and Terry Nichols were convicted and imprisoned...  in the United States.

That Republican  Senators and disgraced former Republican leaders would claim it's too dangerous to hold terrorism suspects in American prisons is not surprising.  What is surprising is that some Democrats and much of the press treat this as a serious objection.  Republicans are grasping at straws to save their relevance.  But everyone else playing along is displaying insanity in the face of the ridiculous.

Look, we already know exactly why the people at Guantanamo are held there rather than on the mainland, and it has nothing to do with safety.  Cheney, Bush, and their administration were bluntly open about their reasons: They wanted a place where the US has complete unquestioned control (like the mainland) but where they can pretend that it's not actually "American soil", so they can claim that legal protections do not apply.

American law clearly applies in the US, but Cheney and Bush's people claimed it does not apply in Guantanamo because it's outside the US, so for example, people held there couldn't ask American courts to rule on their rights.  The Geneva conventions unambiguously require basic humane treatment for all people held in a signatory country's territory, but are ambiguous enough on what is required outside such countries' territory that the Bush administration could cling to the legal fiction that human treatment was not required on Guantanamo.

Most of these reasons have crumbled over time.  The Supreme Court has twice ruled that Guantanamo prisoners do have access to American courts.  The Obama administration has made it clear that the Geneva Conventions requirements for basic humane treatment will be honored.

There are some really dangerous people held in American prisons, but they're mostly gang leaders and mobsters, who have connections to criminals currently active in the US.  Nobody's suggesting we can't hold mafiosos and MS-13 gangsters in American prisons, though. 

If holding terrorists on the American mainland were truly dangerous, they'd have transferred Terry Nichols, Ramzi Yousef, and others out of the country years ago.  These people have been here for well over a decade, and none of the Republicans currently screaming about Guantanamo have ever tried to do much about it.

With an administration that no longer has any interest in pretending that holding people there makes any difference in their legal rights, what's Guantanamo good for now?  Except as a symbol to the world of what the Bush administration believed and did, nothing.

We can continue to have legal disputes about how to handle these prisoners when they're in the US.  There's no reason to keep them at Guantanamo.  Republicans are trying to preserve Bush's legal fictions after they're already dead.