Leslie Morgan Steiner is an advocate and expert on violence against women. She is the author of The New York Times bestselling memoir, "Crazy Love." Her TEDTalk on why victims stay in abusive situations has been viewed by over 4 million people. She serves on the board of the One Love Foundation and DC Volunteer Lawyers Project. She lives in Washington, D.C. The views in this commentary are solely hers.

(CNN) Advocates who speak out against domestic violence debate the value of photos of bruises and strangulation marks on victims of intimate partner abuse. Why do victims need proof? Shouldn't victims' words be believed? But it's hard to look away from the photo of Rob Porter's former wife released to the media, and the yellow-purple bruise that blackens her eye.

Her husband, now a former White House staff secretary, allegedly did that to her, in a hotel room in Italy, 15 years ago, under the most romantic of circumstances. Would you want to be this man's girlfriend, wife, or daughter? Would you hire him, or vote for him? Would you want him working in the West Wing of the White House, controlling all information leading to the commander in chief?

Leslie Morgan Steiner

Of course, everyone's answer is no. And yet, despite two ex-wives with credible, consistent documentation that was shared with the FBI and at least some members of Trump's inner circle, Rob Porter was interviewed, hired and given elite political access into the top echelons of our government. Porter denied the allegations in a statement issued in the wake of his resignation.

Which explains why photographic evidence of abuse is necessary: it breaks through the powerful shield of denial. It's not an exclusive club, the ex-wives of abusive men. The National Domestic Violence Hotline estimates that one in three women are abused in their lifetimes. The challenge is how to break through the general public's ability to know about how common relationship violence is -- but still fail to take action about it.

Relationship abuse thrives when otherwise intelligent, powerful people ignore its warning signs. Visual proof is harder to ignore. In order to stop abusers, and to make powerful enablers like Chief of Staff John Kelly the exception, and not the norm, we all have to better understand how domestic violence unfolds, and the cost we all pay for it.