When pro-Palestinian protesters chant "Palestine from the river to the sea," they are really calling for the "extermination of the Jewish state," one former counterterrorism coordinator warned.

"They think that Israel shouldn't exist at all," Nathan Sales told "Sunday Night in America." "This is exterminationist rhetoric and our First Amendment means that we have to tolerate this kind of speech, but the antidote for that kind of abhorrent speech is more speech. We need to expose what these Hamas sympathizers are really all about." 

Several American cities have seen protests against Israel by pro-Palestinian supporters since the Oct. 7 attack by Hamas. Instead of condemning Hamas, many have spoken out against Israel for military operations in besieged territory, citing civilian casualties. 

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Pro-Palestine rally in New York City

Demonstrators march in support of the Palestinian people on October 8, 2023, in New York City. (Adam Gray/Getty Images)

Sales said now is the time Americans must "stand strong with Israel."

"The attack ... [is] the worst day for Israel in its 75-year history. It's the worst slaughter of Jews since the Holocaust. We've said, ‘Never again.’ Well, now is the time to show that we mean it and the way you show that you mean it is at least being out in the streets and showing support for Jews who are now looking over their shoulders and fearing for their lives."

Sales called on the Biden administration to give their Middle Eastern ally the "diplomatic space it needs." 

"Israel has suffered one of the deadliest terrorist attacks the world has ever seen," he told FOX News. "It needs to degrade and destroy Hamas to the point that it's no longer capable of threatening it militarily or acting as a quasi-government in Gaza. So, what we've heard from the administration is helpful words, but now it's time to see helpful deeds." 

Demonstrators attend an

Demonstrators attend an "emergency rally for Gaza" outside of the Israeli Consulate in New York City, New York on Monday. Supporters of both Palestine and Israel clashed at the event as Israel remains at war with Hamas. (Jennifer Mitchell for Fox News Digital)

Sales implored President Biden to "lock down the southern border" at home in response to a "dramatic spike" in the number of suspected terrorists who have entered the United States – ranging from zero in 2019 to 154 in 2022. 

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"The first priority for any government is to secure its border, to protect its people and we're falling asleep at the job," he reflected. 

"The United States needs to stand strong with Israel and make sure that it is able to finish the job so it never has to face a threat like this again." 

FOX News' Louis Casiano contributed to this report.

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