Bill O'Reilly told Donald Trump tonight that the Republican presidential contender's plan to deport millions of illegal immigrants will never work.

O'Reilly pointed out that immigration law enforcement efforts implemented by President Eisenhower in 1954 resulted in the deportation of one million illegal immigrants.

"Believe me when I tell you, Mr. Trump, that was brutal what they did to those people to kick them back," O'Reilly said. "The stuff they did was really brutal. It could never happen today."

Trump countered that the number was actually closer to 2.2 million, and President Truman also deported 3.5 million illegal immigrants before that.

He added that his plan would deport people in "a very humane way."

O'Reilly insisted that the Supreme Court would rule that every illegal immigrant is entitled to due process in the courts, which would take decades.

Trump disagreed, asserting that the deportation of millions of illegal immigrants wouldn't require a constitutional amendment or any major change to the law, just an Act of Congress.

Watch more above.

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