Clinton made the remarks at a New York fundraising event Sept. 9 where she said about "half of Trump supporters" could be put "into what I call the basket of deplorables." She added, "Now some of those folks, they are irredeemable."
On "This Week," ABC News' Martha Raddatz pressed Kaine on whether it was appropriate for Clinton to use the word "irredeemable."
"You know, that's not a word I would use. I wouldn't use it," Kaine said.
He added, however, "I think we would be unrealistic to think that some people are going to fundamentally change their view."
Kaine also sought to explain Clinton's "basket of deplorables" remark in the context of the birther controversy about President Obama.
"Look, she is very worried, as am I, about the deplorable motivations of those who would question President Obama's citizenship or people who like David Duke who are doing robocalls saying people should vote for Donald Trump. We've expressed it differently, but you have to call out these dark emotions because if you let them pass, you actually can let them grow," Kaine said.
Kaine said he believes "that kind of motivation is reducing" and that not all Trump supporters are driven by these "dark emotions."
"There are other Trump supporters who are really concerned about economic anxieties," Kaine said, arguing that Democrats need to do a better job reaching out to them.
Kaine also discussed the state of the presidential race, acknowledging that the campaign has to do more.
“I always knew this would be tight, and you’re right, we have work to do. We've got to lay out the competing visions of the two candidates,” Kaine said.
He cited the nation's polarized politics as a reason for the tightening polls.
"It has tightened up because I think, Martha, as you know, even with your discussions with voters, we are a divided nation," he said. "We are politically very divided, and that is reflected again and again in so many of our elections.”
As he did on the campaign trail all last week, Kaine used as props his book with Clinton, "Stronger Together," and Donald Trump’s book, “Crippled America,” to contrast the campaign’s two visions.
"A lot of campaigns get very, very engaged and resolved between Labor Day and Election Day, he said. "That just puts the weight on our shoulders to make this positive case the difference between "Stronger America" and "Crippled America" and that’s what we’re going to be doing.”
Kaine forcefully criticized Trump for promoting the false notion that President Obama is not a native-born American citizen, blasting what he called the "bigoted lie" that touches on the "most painful part of the history of this country."
Trump acknowledged Friday that Obama was in fact born in the United States, after years of pushing the “birther” conspiracy.
"This is so painful to so many Americans because they remember our history," Kaine said. "An African-American was not allowed to be a citizen, whether slave or free, born here or born elsewhere, until we fought a Civil War and enacted the Fourteenth Amendment to the Constitution,” Kaine said.
"I hope someone will ask Donald Trump, 'When you were doing that, did you believe it, and if you believed it, how could you have been so gullible or conspiratorial, or if you didn’t believe it, what were you doing dragging us back to the most painful chapter of American life? Who were you trying to appease by doing that?' That question still needs to be answered."