The word “opportunist” gets kicked around a lot in “Whitney,” director Kevin Macdonald’s new onstage/backstage, warts and all documentary about Whitney Houston.

This family member tosses it at that family member, or girlfriend, music industry professionals slap it on Houston’s father, her family entourage, so many of them on her payroll treating her like, as one eyewitness puts it, “their ATM.”

Some reviews of the film apply it to director Macdonald, for focusing on the sensational, the sordid and the before-our-eyes tragedy of Houston’s very public decade-long decline and death in 2012.

I found “Whitney” to be shockingly emotional just in the way it presents this once-in-a-lifetime voice, her seemingly effortless talent and the personal cost a life of secrets, disappointments and addiction. She found fame beyond modeling with her gift-from-Mama (Cissy Houston) voice, and drugs long before Bobby Brown.

The most damning revelation in the film is that the girl nicknamed Nippy who grew up to be the greatest pop starlet of her era wasn’t just self-destructive. As in the much-honored Amy Winehouse doc “Amy” of a few years back, our heroine is shown to have had a lot of enablers, chief among them, like Amy, her own father — John Houston.

She lit up rooms, concert stages and “The Bodyguard” with her smile, stormed the pop charts with her talent and stared down accusations from a homophobic African American community that she was gay, or “too white.”

Yes, it’s fun to recall that “opportunist” Rev. Al Sharpton led a boycott, calling her “White-ney,” in the ’80s, and that the shill was the first guy on the phone to be interviewed by CNN when she died. She had to declare she wasn’t gay on chat shows and that she wasn’t an addict to Dianne Sawyer, lying both times.

She was booed at the “Soul Train Awards,” dated footballer Randall Cunningham and was “dogged” by Robert DeNiro. Her first love and longtime protector and most trusted confidante, Robyn Crawford, was eventually chased out of her life by her controlling Dad and ego-bruised, and bruising husband Bobby Brown.

She was, by any objective measure, a fatally disastrous parent.

But her vocal range dazzled, her smile invited all in and if you ever doubted her crossover appeal, there was that Gulf War era Super Bowl appearance where her “Star Spangled Banner” moved all of America to tears.

When she was in trouble, churches held prayer vigils to pray for her recovery, rehab and restoration.

Macdonald, still best-known for “The Last King of Scotland,” but who did the equally thorough Bob Marley bio-documentary “Marley,” sums up this life within its very personal parameters. He interviewed scores of friends, employees, collaborators, relatives and business partners, from the prickly Bobby Brown to record label chief L.A. Reid and “Bodyguard” co-star Kevin Costner.

Personal assistant Mary Jones will break your heart with the tears she still sheds over Houston’s inglorious end.

Whatever pushback this film is getting should be taken with a grain of salt. The denial of this gospel singing daughter of a gospel singer’s problems, flaws and complicated love life within that corner of African America is both dated and delusional. She was “fluid” in her sexuality, negligent as a parent and incapable of “praying away” the addictions that tie themselves to too many of those gifted with the kind of fame she dealt with.

A confidante who recalls her visits with Michael Jackson, because sometimes each tabloid famous famous singer needed just to be in the room with someone facing the lonely world through exactly the same eyes, is terribly touching.

Macdonald uses news footage of her era to illustrate the passage of time, and home videos, “backstage” documentary footage never meant to see the light of day (Janet Jackson/Paula Abdul bashing), grainy home video and movies to tell her story. If the film has a serious shortcoming, it is Poverty Row studio Roadside Attractions’ not digitally cleaning this stuff up. It’s an ugly looking film, and the murky video gives it a seamy “True Crime” TV documentary feel.

I recall talking with Macdonald when “Last King of Scotland” came out, asking him off-handedly what he was doing next and being shocked that the Scotsman was planning an epic look at the life, music and legacy of Jamaican reggae icon Bob Marley. I interviewed him again when the film came out and asked why he’d want to endure the “What could YOU know about Bob Marley?” abuse that was sure to follow.

Oh, he reassured me, he’d only go through THAT for a “singular talent, a huge figure in the culture” like Marley.

With “Whitney,” you appreciate Macdonald’s own talents, his eye and ear for icons and his unflinching way of challenging (we hear pointed questions for Brown and others, off-camera) the people who knew her to give him the straight dope — not just sycophantic, self-serving plaudits.

Houston was a real mess, to be sure — probably abused as a child, certainly abused as a wife, ill-used by her crooked Dad, not saved by friends, family or the industries that made fortunes off her. But she was a “singular talent, a huge figure in the culture.” “Whitney” is a touching naked look at how that American Tragedy played out. 

MPAA Rating:  R for language and drug content

Cast: Whitney Houston, Bobby Brown, Gary Houston, Mary Brown, Kevin Costner, L.A. Reid, Lynne Volkman Credits:Directed by Kevin Macdonald. A Roadside Attractions release.

Running time: 2:00