Washington (CNN) Add Fox News host Bill O'Reilly to the list of those critical of Sen. Rand Paul.

O'Reilly joined the chorus of voices slamming the Republican from Kentucky on Tuesday for his comments that vaccines should not be mandatory and took the chance to take another swipe at the libertarian-leaning senator's foreign policy, calling him "perhaps the most controversial candidate in the race."

"That's not unusual for me disagreeing with Mr. Paul," O'Reilly said.

The conservative host also called Paul's stance on terrorism and Iran "naïve," reprising previous comments that Paul's foreign policy views would hurt him in an eventual GOP primary.

Paul opposes the GOP-led effort to impose additional sanctions on Iran in an attempt to pressure the Iranians to give up their nuclear program.

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