Sen. Tom Cotton (R-Ark.) tonight fired back at a lawyer for 9/11 mastermind Khalid Sheikh Mohammed over Guantanamo Bay.

Cotton made headlines last week when he grilled a Pentagon official over the prison.

"In my opinion, the only problem with Guantanamo Bay is that there are too many empty beds and cells there right now. We should be sending more terrorists there for further interrogation to keep this country safe. As far as I'm concerned, every last one of them can rot in hell. But as long as they don't do that, they can rot in Guantanamo Bay," Cotton had said.

Sheikh Mohammed’s attorney called Cotton’s remarks “shameful” and said that they could impact Americans overseas.

Cotton responded to this tonight, saying that the nation’s enemies don’t need an excuse to treat American captives badly.

Megyn Kelly noted that some people say the U.S. can’t hold Gitmo detainees in perpetuity.

“They’re not American citizens, they’re terrorists,” he said. “They’re not entitled to the legal rights of American citizens. If they didn’t want to be detained indefinitely, they shouldn’t have taken up arms against America, they shouldn’t have helped mastermind the terror attack that killed 3,000 Americans. And if we release them, then you can be sure a large number of them will return to the battlefield,” he said.

Cotton noted that some estimates have found that one-third of released Gitmo detainees have returned to the battlefield, which is why it’s important to keep Gitmo open.

“We should be proud of the way we’ve treated these savages at Guantanamo Bay and the way our soldiers conduct themselves all around the world to include the people who are doing the very hard work at Guantanamo Bay,” he said.

Watch more above.