The "X-Men: Apocalypse" actress only learned Steven Wilder Striegel had a criminal past last month, as she prepared to embark on a promotional tour, and she immediately took the shocking discovery to bosses at Twentieth Century Fox.
She accused director Shane Black of keeping the news from the cast and crew, as his pal Striegel, who appears in a small scene with Munn, had served time behind bars for trying to coax a 14-year-old girl into a sexual relationship over the Internet in 2010.
Fox chiefs soon cut Striegel's appearance from the finished movie, but Munn reveals she was initially left hanging when they took their time responding to her first complaint.
"When I called, (Fox) was silent for two days," she told Variety at the Toronto Film Festival in Canada, where "The Predator" premiered over the weekend (September 8-9).
"I did have to reach out again and say I didn't feel comfortable presenting at the MTV (Video Music) Awards with Keegan (Michael Key, co-star) unless this guy was out of it."
However, Olivia clarifies, "I'm not saying they weren't working on it behind the scenes. I just didn't hear anything about it. But I'm happy that they did obviously because I'm proud of the work we did in this movie, we all worked really, really hard, and I wouldn't be able to morally stand behind this movie with this guy in there."
Fox executives insisted they were unaware of Striegel's felony convictions, which were made public in an article in the Los Angeles Times last week (ends September 7), while Black eventually apologised for not letting his colleagues know, claiming he had been misled by his friend over the seriousness of the incident.
Munn felt compelled to report the news to studio bosses "because movies are so far reaching."
The actress claims she has nothing against giving Striegel a second chance, but explained, "I do have a hard line when it comes to people who hurt children or animals. You deserve to go make money, but not alongside me in a film. You can go work in a lot of other places or like make an Etsy (online) store or something."
And she is a little disappointed in Black for not reaching out directly to her after the controversy.
"I think an apology has to happen privately not just publicly," she said. "I believe in his apology that he said he (apologises) to everyone past and present that he's put in that situation, and that would be me, but I didn't get that apology, I read about it online like everyone else."