“Radical” is the last word most people would associate with Fred Rogers, the mild-mannered, cardigan-wearing children’s TV host who was the epitome of straitlaced normalcy.

However, one viewing of “Won’t You Be My Neighbor?,” the eye-opening new film by Oscar-winning documentarian Morgan Neville (“Twenty Feet From Stardom”), shows how pioneering, how groundbreaking, how downright revolutionary Rogers’ gentle yet powerful message of kindness and goodness was — and continues to be — in this often cruel and uncaring world.

There are surprises aplenty in Neville’s documentary, but here are five things most people probably don’t know about Rogers that the movie discusses:

1. Putting puppets in a children’s TV show wasn’t planned.

Rogers, a Presbyterian minister, was appalled by the state of children’s television in the 1950s, all pie-in-the-face slapstick and rapid-fire cartoons. He went to work for the public TV station in Pittsburgh, WQED, on a show called “Children’s Corner.” The show was live and unscripted, and once when a technical glitch stopped the show, he put a puppet on his hand and pushed it through a paper backdrop. The puppet was a tiger, later named Daniel Striped Tiger — which became Rogers’ gentle alter ego on “Mister Rogers’ Neighborhood.”

2. Rogers almost single-handedly saved public television.

In 1969, when the Nixon administration was looking to cut funding to the fledgling Corporation for Public Broadcasting, Rogers gave heartfelt and impassioned testimony to a Senate subcommittee. He quoted lyrics from the songs he wrote for his show and explained his philosophy of giving children positive messages on TV. The notoriously impatient chairman, Sen. John O. Pastore, D.-R.I., was moved and declared, “You just earned the $20 million.”

3. Rogers tackled big issues, like racism and violence.

Neville deploys some moving clips from Rogers’ show in the film. In one tender scene, which aired just days after Robert Kennedy was killed in 1968, Daniel Striped Tiger asks Lady Aberlin (Betty Aberlin), “What does ‘assassination’ mean?” In another, Rogers soaks his feet in a wading pool. His friend Officer Clemmons walks by, and Rogers asks Clemmons, who is African-American, to beat the heat by putting his feet in the pool with him. It was a simple gesture, but a meaningful one in an era when black people were barred from many public swimming pools. (The moment ends with Rogers toweling off Officer Clemmons’ feet, as Jesus did.)

4. Rogers wasn’t so progressive on some issues.

In an interview for the film, François Clemmons, the actor who played Officer Clemmons, describes an incident when Rogers learned that Clemmons had been spotted in a gay bar. Rogers firmly told Clemmons that he could not frequent gay establishments if he wanted to stay on the show — and his homosexuality was never discussed on the show. Joanne Rogers, Fred’s widow, explains that Fred eventually came around, but “François was too early.” (Clemmons also dispels a long-standing rumor: Rogers didn’t have a gay molecule in his whole body.)

5. He was beset by doubts and fears of failure.

Neville chronicles not only the successes of “Mister Rogers’ Neighborhood,” but also Rogers’ failures — like a short-lived interview series for adults, “Old Friends … New Friends.” When he was asked to record a public-service announcement for children after the 9/11 attacks, he had to be reassured that anyone would listen.

While providing these revelations and many more, Neville suffuses “Won’t You Be My Neighbor?” with Rogers’ overarching message of love. As Rogers himself says in one archival interview: “Love is at the root of everything. All learning, all relationships. Love or the lack of it.” It’s a message we often forget these days, and a message we all need to hear loud and clear.

★★★½

Won’t You Be My Neighbor?

The life and philosophy of Fred Rogers, children’s TV pioneer and fundamentally decent human being, is captured in this charming, thoughtful documentary.

Where • Salt Lake-area theaters.

When • Opens Friday, June 22.

Rating • PG-13 for some thematic elements and language.

Running time • 94 minutes.