Sex has always been one of the great taboos in modern culture. The act, or at least the desire, is something most adults have experience of, yet in polite society it is still something that remains alluded to rather than discussed. Sex With Sue is a documentary about someone who broke those barriers, and in doing so helped a lot of people.

The Sue in question is Sue Johanson, a registered nurse from Toronto. While raising her children, she discovered she couldn’t answer many of the questions they and their friends had. After educating herself, she became a public speaker, taking useful, healthy sex education to schools and public spaces. Her demeanour as an eccentric, grandmotherly figure talking openly about pleasure led to radio and then television fame in the ’90s and ’00s.

Like other documentaries about Fred Rogers or fellow ‘sexpert’ Dr Ruth, this warm movie is the story of an unusual icon. Someone who strode bravely into the limelight with a mission, helping people in a way that was desperately needed at the time. Through a very standard method of archive footage and talking head interviews, we follow Johanson from the Toronto suburbs to New York, where she achieved US fame after being discovered by Oprah Winfrey.

It’s a tale of two parts, really. Firstly, there’s the woman herself. Unflinching in her pursuit to help people, it’s fascinating to see Sue become so beloved, as well as the string of educators and entertainers who cite her as an influence. The recognisable may be Canadian stand up Russell Peters, a self-professed fan of her radio, but the majority of interviews are those who knew and loved her.

There’s a lot of fun to be had watching this matronly older lady (she started her national TV show, Talking Sex, in her mid-’60s) talk about dildos and orgasms, as well as being chauffer driven to The Tonight Show in Manhattan, wearing her comfy coat and large glasses. It’s also charming to see her ease the concerns of her callers. The queries range from innocent education, such as a caller who feels threatened by his partner’s vibrator; to more complex requests such as a lesbian couple wanting to know the right time to remove anal beads. It’s all met with a calm and supportive nod from Johanson, and relieved thanks from the anonymous viewer.

For those whose sex education came post-Google, it’s a reminder that a world of information wasn’t always available at the touch of a button, which leads to the second part of the documentary. Sue’s rise came at the time of a reckoning in sexual health in the United States, where Johanson had a second Sunday night call-in. We see how the Aids epidemic was made so much worse by a lack of information, by demonising the gay community instead of offering information that would save their lives. Equally, issues like abortion in North America meant millions of young women had no idea of their options, making Sue and other community educators a lifeline. Johanson and the film’s argument, that wrapping sex in shame does more harm than good, is hard to disagree with.

As with most tribute documentaries, criticism is in short supply. There is an admission that the rise of the internet put her in a curious position where achieving her goal made her obsolete. People were more savvy about sex, to the point where identities had developed beyond her understanding.

Nonetheless, the importance of educators in our lives is still the pertinent heart of this tribute. Sex With Sue chuckles at sex, with the understanding that it should be fun. Johanson, who filmed interviews for the documentary prior to her death in June, remains a fascinating subject whose colourful personality belies just how many people owe her thanks.

Sex with Sue premieres at the 31st Raindance Film Festival.