On more than one occasion, the late co-founder and co-president of Housing Works Keith Cylar told me that the biggest threat to his existence was not asthma, which almost killed him as an infant and several more times throughout his life, nor drugs, to which he was addicted for most of his adulthood, nor AIDS, which he lived with for over 20 years, nor homophobia, which he confronted almost every day from the time he came out as a teenager.

The biggest threat to his existence, he said, was being a Black man living in America. I could not shake those words last night and again this morning reading and watching the videos of the police killings of Alton Sterling in Baton Rouge and then of Philando Castile in Minneapolis. And I asked myself, why does this keep happening time after time after time after time?

Of course, I know the answer to that question. If there is anything that we have learned over the last eight years with a Black man as our President, and if there is anything we have witnessed over the last year as Donald Trump has risen to become the presidential nominee of the Republican Party, it is that racism is not just something in our past.

Rather, it is seeded in the DNA of our nation and in the DNA of every city, town and hamlet in our land. It touches and taints everything around us. It is why Black women are so many times more likely than other women to have HIV, especially in the Deep South, and it is why young Black men who have sex with men are more likely to have HIV than any other group right here in New York City.

It is why people of color, and especially Black people, fare worse on almost every health indicator, and every other measure of well-being. Yes, there are other deeply seated “isms” in our society, including sexism, homophobia and transphobia, but look at any one of these other prejudices through the prism of race and you can see just how utterly devastating racism really is.

We bear witness to this every day as we watch how the people we serve here at Housing Works are beaten down and mistreated by the police, by the corrections system, by the courts, and by almost every other system they touch.

Whether that mistreatment is associated with their use of drugs, their homelessness, the actions they engage in to survive or their sexual orientation or gender identity, all of it is inevitably tainted by racism that tears at their souls, destroying self-esteem and depriving people of hope for a better life.

To be sure, not every police or corrections officer, judge or prosecutor, welfare worker, and the like is racist. Many are good, loving, caring people. But they operate in systems that not only afford power over people’s lives, but that also tolerate and even facilitate racism by their very lack of accountability.

According to the Daily News, Alton Sterling was a homeless man, living in a shelter, and making his living selling CDs in a parking lot. Philando Castile was not homeless. He worked at a local public school as the cafeteria supervisor. Both Sterling and Castile were fathers, who, notwithstanding anything else, were deeply involved in the lives of their children.

Yet each was approached by the police as nothing more than a criminal, a person to be feared or despised, a person whose life was expendable. And the same has been experienced by so many Black men and other men of color, especially those who are young, that it truly is the norm. Each encounter with the police is fraught, even if only a relatively few end in death. And each fraught stop leaves a scar that may not easily heal.

Racism is something that is hard to challenge. It makes us feel defensive, and it is so pervasive that we often feel helpless to do anything about it. But the one thing we cannot do is to pretend it doesn’t exist.

We have to address it if we want to live up to our commitment to be healing community. We have to address it if we want to end AIDS as an epidemic. And we have to address it if we ever want our city, our state, and our nation to come close to living up to their promise. One thing we certainly cannot accept is police stopping men, searching men, arresting men, and shooting men because they are Black.

One of my favorite singing groups of old is Sweet Honey in the Rock, founded by Bernice Johnson Reagon, who was one of the Freedom Singers during the height of the civil rights movement. This morning, while running in Central Park, my mind sang over and over a verse and the chorus of “Ella’s Song,” which Reagon authored: “Until the killing of Black men, Black mothers’ sons, is as important as the killing of white men, white mothers’ sons, we who believe in freedom cannot rest. We who believe in freedom cannot rest until it’s won.”

Housing Works and scores of other groups gathered Thursday, July 7, at Union Square in Manhattan to raise our voices together.

Charles King is CEO of Housing Works. This article was originally published on the Housing Works website.