She said it was an important movie.
"I just can't think of anyone else who could make this film… he played Adolf Hitler."
"I think we should all be proud of him."
On coronavirus
Ardern said 157 people are isolated in New Zealand.
She said frequent medical checks are being undertaken.
She said there are still no cases of coronavirus in New Zealand.
Border restrictions, she said, have now been reviewed three times.
She said there have been "very few" people attempting to come to New Zealand who have been turned away.
She said much of the economic impact of coronavirus cannot yet be quantified.
She said 13 per cent of New Zealand's tourism comes from China – she said Tourism NZ are working with IRD to help "ease the pressure" for some of the small businesses affected by the tourism downturn.
On political donations
Ardern said she said it was her strong very that "we should have a strong look" at New Zealand's electoral finance laws.
But she said that would happen after the election.
She would not be drawn on the fact NZ First is reviewing its donation rules, saying "that's a matter for them".
Radio NZ
On the issue of Concert FM, Ardern said Cabinet would look at ways of making sure it won't go off the FM frequency.
Under the proposal put forward by RNZ's top brass, Concert would be taken off FM radio on May 29 and the youth platform would be phased in ahead of its full launch on August 28.
The Government has come under pressure from the likes of former Prime Minister Helen Clark, and her then Finance Minister Michael Cullen.
A petition calling for RNZ to ditch its plans to scrap Concert has already received more than 10,000 signatures.
Speaking to Newstalk ZB this morning, Ardern said she was the Government has been "pretty frustrated by this situation."
"To say I've been a little bit miffed by the situation would be an understatement."
As well as being Prime Minister, Ardern is also the Minister of Arts, Culture and Heritage – because of that, she said she feels very strongly about the issue.
"I understand that RNZ has obligations to all New Zealanders, and it is their view that they are not catering for one sector," she told RNZ.
"But it is my view as arts minister that one does not need to come at the cost of another."
The issue was likely to have been discussed at Cabinet this afternoon.