The Aaron Sorkin-created series follows the staff of the fictional Atlantic Cable News, starring Jeff Daniels as news anchor, Emily Mortimer as the executive producer, Alison Pill as associate producer and Munn as financial analyst.
The Newsroom received mixed reviews after its season premiere on June 24 from critics at The Washington Post, The New Yorker and The New York Times.
Munn told New York Magazine's Vulture: "I know the critics are also saying the show's smug, that it's like Monday morning quarterback. I understand that.
"If you're looking at it as Sorkin trying to tell us how to do the news, and this is how we should have done it better, I get it. There's an element of that. And there's some naïveté, but that's why it's a drama.
"I'm an ex-journalist. I majored in journalism and I worked in local news stations. My first job was on the assignment desk of an NBC station in Tulsa, Oklahoma. I truly believe nobody goes into journalism to report on the latest celebrity pregnancy or sensationalise the murder of a child. They want to provide the people with vital information.
"Sorkin loves journalists, loves the media, loves the news. I don't believe the show is his soapbox for him to lecture the media on how to be better. On the contrary, I believe his show is an opportunity to help the audience fall in love with the news again. I felt bad for Aaron."
Another Newsroom star previously defended the series, which was recently renewed for a second season.
Sam Waterston, who plays the news division president, said that the show isn't "preachy" but is "aspirational".
The Newsroom airs on Sundays at 10pm ET on HBO. It is set to debut in the UK on Tuesday (July 10) at 10pm on Sky Atlantic.
Watch a trailer for The Newsroom below: