WATCH: Mass walkout before Netanyahu speech prompts fiery response from Israeli prime minister

After taking the stage, Netanyahu said, "Before I begin, just a quick announcement, if there are any other moral cowards who haven't yet left this hall, please do so now," as cheers erupted from the remaining delegates in the chamber.

"Now, you want to hear the ultimate irony?" he continued. "In defending itself, Israel is also defending many of the countries whose delegates just left this hall. In fact, I want you to know that many of the leaders even thanked us privately for taking out Iran's nukes."

"It's hard to imagine more mind blowing hypocrisy, but that's exactly what it is," said Netanyahu.

Despite the protests, the prime minister delivered a defiant message, telling critics, "You don't know what you're talking about."

He cast Israel's fight as one for its own survival and the survival of all the world's nations against "barbarians."

"For the past three years, our heroic soldiers have fought day in an day out in a seven front war. Do you know any other country the size of New Jersey capable of fighting a seven front war? And for three years, seven fronts Hamas, Hezbollah, the Houthis, Iran, militias in Iraq, militias in Syria, Palestinian terrorists in Judea, Samaria, they all ganged up on us to wipe us off the face of the earth, they failed. Because instead of collapsing, we delivered crippling blows to all of them, with our great American friends."

"To the protesters outside, to the hypocritical delegates who left this hall. I ask, 'Where were you when the Iranian tyrants butchered and maimed tens of thousands of unarmed Iranian civilians? When they butchered and maimed thousands of their own people? Where were you? Did you organize mass rallies, hunger strikes? Did you protest outside the Iranian mission to the UN? Did you speak out for that matter, for Christians persecuted in Iran and throughout the Middle East?' No, no, you didn't, because you're phony human rights protesters," he said.

He also thanked President Donald Trump for ordering U.S. action against Iran.

"In this battle against the barbarians, we've had no greater partner than President Trump," said Netanyahu. "I thank him. I thank him for his bold leadership. He boldly confronted an enormous danger to America, Israel and the world."

"He understood that if left unchallenged, the fanatic ayatollahs who chant, 'Death to America, death to Israel,' would eventually carry out their mad fantasies. So, Israel and America acted together not only to protect ourselves, but to save civilization," he said.

Netanyahu also criticized detractors in what he called "the eigth front in this war," which he said is "the war for truth." He said that this "war" is "waged in the world's media and most perniciously, in social media."

Turning to criticism from U.S. figures, Netanyahu called out New York City Mayor Zohran Mamdani, a socialist, whom he called "anti-semitic," as well as influencer Hasan Piker. Addressing Mamdani directly, Netanyahu said, "Mr. Mamdani, you try to stop me from coming here. You tried to silence me. Well, you can't silence me. You can't silence the truth."