WATCH: Bill O'Reilly tells Stephen Colbert that Trump's "using this terrorism issue ... to bolster his popularity"

"O'Reilly Factor" host Bill O'Reilly guested on Stephen Colbert's "Late Show" last night, with the two primarily discussing the weekend's mass shooting in Orlando.

O'Reilly's response to the massacre, reflecting the sentiment of his Republican viewership, was to suggest Congress pass a declaration of war against ISIS.

"If you make a declaration of war, it does a number of things," O'Reilly explained. "Number one, it gives your authorities inside the United States far more latitude to detain [Orlando gunman] Omar Mateen."

O'Reilly added (to smattered boos) that "FDR did it with the Japanese."

Such a historically problematic policy suggestion reeks of GOP nominee Donald Trump's Muslim ban. However, O'Reilly lessened Trump's response to the shooting as "a political response."

"He's using this terrorism issue ... to bolster his popularity," O'Reilly said. "Trump is bringing a robust, 'I'm gonna get these guys' attitude to the table [while] Mrs. Clinton is bringing a more nuanced situation."

Watch the interview below: