"Why does President-elect Trump again and again and again take it upon himself to be Vladimir Putin's defense lawyer rather than listening to and respecting the intelligence professionals of the United States," Kaine told CNN's Alisyn Camerota on "New Day" in his first national interview since the 2016 presidential election.
The former Democratic vice presidential nominee, a member of the Senate Armed Services Committee which is hold a hearing on hacking Thursday, said that even if Trump believes Russia can be America's ally in the fight against ISIS, he doesn't have to "trash" American intelligence professionals in the process.
"There is something very unusual -- indeed, even sort of suspicious -- about the degree to which he casually kicks aside the intelligence community when he won't even go to the briefings again and again and takes the Assange/Vladimir Putin line on this important question" about whether Russian was behind the election-related hacks, Kaine said.
California Rep. Adam Schiff, a member of the House Select Committee on Intelligence, said Republicans' confidence in Assange over the intelligence community is "embarrassing."
"You hear former colleagues like mine, Vice President-elect Mike Pence, tie themselves in knots, or my colleague (California Republican) Darrell Issa, saying they put more faith in an accused sex offender than their own intelligence agencies," the Democrat told Chris Cuomo on "New Day."
"It's embarrassing to be honest with you," he added. "This is not healthy skepticism as they would like to portray it. This is very unhealthy, essentially avoidance of the facts."
Schiff also said he didn't expect Trump to change his tune after he receives an extensive intel briefing on the hacking on Friday.
"He has been briefed, he knows better," Schiff said. "It's at odds with his own preferred version of events, and he will not accept it."
He added, "I think it goes back to a very simple thing. It's not unrelated to Julian Assange. That is during the campaign, WikiLeaks was helpful to him, Assange was helpful to him. During the campaign, the Russian hacks were helpful to him, and Donald Trump does not bite the hand that feeds him."
Trump's ongoing feud with the intelligence community just weeks before his inauguration suggests that there will be unusual tension between the White House and America's top spies on national security issues. When the President-elect enters office, he would have invested more credibility in the head of Russian and the fugitive who founded WikiLeaks than leading US intelligence agencies.
"When he's quoting Julian Assange, who is wanted for sexual assault crimes
in Sweden, as some kind of authority on this, that makes me really scratch my head," Kaine said.
Assange is wanted by Swedish authorities over allegations of sexual assault, and was granted asylum at the Ecuadorian Embassy in London in 2012.
But Trump pushed back Thursday against the idea that he is in agreement with Assange.
"The dishonest media likes saying that I am in Agreement with Julian Assange - wrong. I simply state what he states, it is for the people," he tweeted.
"to make up their own minds as to the truth. The media lies to make it look like I am against "Intelligence" when in fact I am a big fan," Trump added.
The Virginia Democrat also blasted Trump for encouraging Putin to interfere in the 2016 election.
During a July speech, Trump said
, "Russia, if you're listening, I hope you're able to find the 30,000 (Hillary Clinton) emails that are missing."
Kaine believes Russia took the President-elect up on the invitation. "That's exactly what happened. We've got to get to the bottom of this because we've got to make sure it doesn't happen again," he said.