Charles Fried, a Harvard Law professor and a former U.S. solicitor general, sharply criticized President Trump's conduct and accused Attorney General William Barr of lying about the Russia investigation.

"It is the very opposite of the great Republicans ... like Ronald Reagan, like Dwight [Eisenhower] -- can you imagine Dwight Eisenhower speaking the way this man speaks?" Fried, who served under Reagan's administration, told MSNBC host Chris Hayes Thursday.

The MSNBC host had just asked how he and others have been reacting to "what is happening with this president and the rule of law." Fried said people were "horrified."

Fried then asked Hayes if he could imagine former President Abraham Lincoln speaking the way Trump did. "This man is ignorant," he said.

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Fried's comments came on the same night that Trump held a rally in which he used profanity to insult former Vice President Joe Biden and mock former FBI agents Peter Strzok and Lisa Page.

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"He was only a good vice president because he understood how to kiss Barack Obama's a--," Trump said of the former vice president.

Page and Strzok have long been on Trump's radar as they sent controversial texts about Trump around the time the FBI was investigating Russian meddling in the 2016 election.

When former Special Counsel Robert Mueller released his report, he concluded he didn't have sufficient evidence that Trump's campaign met the legal definition of "conspiracy."

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Fried, on Thursday, also took aim at Attorney General William Barr, who released a summary of the report before the Justice Department ultimately released it.

"Bill Barr lied about what that report said when he thought that we weren't going to see it," he told Hayes.