Ms Leverkuhn - who is also known as Mara Rotudu - has been suspended from Labour after launching a series of controversial online attacks in which she suggested the internationally-recognised IHRA definition of antisemitism was a "masterful tool for crushing dissent".
She also wrote that "ceding ground to antisemitism smears was an error", adding that the "fabrications" need to be confronted.
In another article she wrote of "Fake antisemitism, Zionism and fear of speaking out."
Ms Leverkuhn's case has been deemed so serious by Labour officials that it has been referred to the party's highest disciplinary body to rule on.
Mr Williamson conducted his interview with Ms Leverkuhn only two weeks ago - before the hearing reached Labour's disciplinary panel last week.
Referring to Ms Leverkuhn's background in a former Communist state, "with an experience of what tyranny was like", Mr Williamson added: "Obviously, it's something we need to be mindful of and vigilant about.
"We on the left absolutely have to champion freedom of speech because if we don't, then the potential consequences further down the line... would be compromised as a consequence of that."
Mr Williamson's interview was published by the far-left magazine The Word, with a clip released on You Tube last Thursday after the MP's suspension from Labour was lifted.
