He got into a discussion with Senator Cory Booker about the difference between apology and atonement after agreeing that Tim Kaine wasn't an Israel basher and that former President Obama wasn't an actual anti-Semite.
In his writings, he has called members of J Street, a liberal Jewish group, worse than "kapos", a word for Jews who collaborated with the Nazis during the Holocaust.
But the organization which suffered from his harshest criticisms, J Street, has not received a call. "My regret is that I did not express my views respectfully".
David Friedman, a bankruptcy lawyer and longtime friend of Trump, said he regretted calling former President Barack Obama anti-semitic and disparaging the entire State Department and large swaths of liberal Jews. Republicans largely sought to play to the Trump nominee's strengths, while Democrats aimed for weak spots. Sen. Rubio argued the USA should be unashamedly pro-Israel, noting that the Jewish state is America's staunchest ally in the volatile Middle East.
Yoni Fromwitz, who works at the Tefillin factory in Beit El, said he believes Friedman will keep his personal feelings in check if he becomes ambassador.
Multiple senators pressed Friedman over whether the U.S. had abandoned the two-state solution formula.
Social media users have also criticised Friedman's nomination under the hashtag #RejectFriedman. He also cautioned against the expansion of settlements in the West Bank.
"I find this whole process to be unreal, this sort-of ordeal you're being put through to account for all these words, in particular given some of the groups that are ratcheting all this up", Rubio said.
"We believe him to be unqualified for the position", wrote the former ambassadors, including Thomas Pickering, Edward Walker, Daniel Kurtzer, James Cunningham and William Harrop.
Speaking just a day after Trump broke with decades of American foreign policy by not explicitly endorsing a two-state solution during a joint press conference with Prime Minister Benjamin Netanyahu, Friedman said a two state solution still represented the "most ideal" resolution to the conflict. CUFI spans all fifty states and reaches millions with its message.
At a high-profile White House meeting on Wednesday, Trump abandoned those positions. The Palestinians and the worldwide community have long favored the establishment of an independent Palestinian state.
"I'm looking at two-state and one-state, and I like the one that both parties like", Trump said, adding "If Israel and the Palestinians are happy, I'm happy with the one they like the best". "Anybody that wants to say the United States doesn't support a two-state solution, that would be an error". But the alternatives appear to offer dimmer prospects for peace, given Palestinian demands for statehood.
During an exchange with Sen. Tim Kaine about the prospects of a one-state outcome to the conflict, and whether he could confirm the U.S. would not abide a situation in which the Palestinians are "deprived of full and equal legal rights", Friedman responded in the affirmative, saying: "I think so".
"I'm having difficulty understanding your use of those descriptions and whether you really can be a diplomat", Cardin said. "I don't know Israelis on the right- even on the far-right- who would support that". He said most Palestinians are "being held hostage by a ruthless regime", a reference to the Islamic militant group Hamas, which seized power there in 2007.
At least six protesters were escorted out of the hearing during the first half hour of the hearing for interruptions. Two men, minutes apart, stood and shouted pro-Palestinian slogans.
Another protester declared, as he held a Palestinian flag "We were there, we are there now, and will always be there".
Hecklers take aim at David Friedman. "He is a war criminal!"