Deeming waterboarding "torture," President Barack Obama's administration discontinued its use during his first term in office. Proponents of the controversial practice, as The Washington Post's Jenna Johnson noted, avoid labelling it as torture, which would violate various international laws and treaties. Trump, meanwhile, has not only pledged to reinstate waterboarding, but also introduce other methods of interrogation that are "so much worse" and "much stronger."
"Don't tell me it doesn't work - torture works," Trump told the Sun City retirement community. "Okay, folks? Torture - you know, half these guys (say): 'Torture doesn't work.' Believe me, it works. Okay?"
Trump has also said on multiple occasions that the United States should kill the family members of terrorists.
"That will make people think. Because they do not care very much about their lives, but they do care, believe it or not, about their family's lives," Trump said during a debate of Republican presidential candidates in December.
Politifact has pointed out that targeting terrorists' family members is barred by the Geneva Conventions.
During his appearance on "Real Time," Hayden cited Trump's pledge to kill family members as being among his most troubling campaign statements.
"That never even occurred to you, right?" Maher asked.
"God, no!" Hayden replied. "Let me give you a punchline: If he were to order that once in government, the American armed forces would refuse to act."
"That's quite a statement, sir," Maher said.
"You are required not to follow an unlawful order," Hayden added. "That would be in violation of all the international laws of armed conflict."
"You've given us a great reason not to support Trump. There would be a coup in this country," Maher joked.
Hayden said he didn't mean to imply that the military would provoke "a coup."