Alan Dershowitz said former Trump attorney Michael Cohen doesn't seem to understand the difference between what's wrong and what's illegal.

The Harvard Law professor emeritus and author of "The Case Against Impeaching Trump" appeared on "America's Newsroom" Friday to weigh in on a new "Good Morning America" interview in which President Trump's self-described former "fixer" said that the president knew hush-money payments to Stormy Daniels and Karen McDougal were wrong.

Cohen was sentenced to three years in prison Wednesday for a range of crimes, including tax evasion, campaign-finance violations and lying to Congress.

When asked by host George Stephanopoulos if Trump knew it was wrong to make the payments, Cohen replied, “Of course,” and added that the purpose was to “help [Trump] and his campaign.”

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"Reasonable people can disagree about whether it's wrong to pay hush money to somebody to stop them from disclosing alleged improprieties sexually. Reasonable people can say that's wrong or that's right. It's not illegal," Dershowitz said.

He explained that a presidential candidate could give cash to an individual and explicitly state not only that the payment is to buy their silence about alleged improprieties, but also that it is specifically designed to help their campaign, and that still would not be a crime.

"Whether you think it's wrong or right, I don't understand the case for how it's illegal," Dershowitz said. "If you look at the very, very complicated campaign laws, the one thing that comes out simply is that a candidate may himself or herself contribute as much as they want to a campaign."

He warned against "criminalizing political sins," arguing that blurring the line between "wrong" and "crime" endangers the rule of law.

Watch more from Dershowitz above, and don't miss Geraldo Rivera's fiery reaction to the new Cohen interview.

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