(CNN) Brandon Stanton, the blogger and photographer behind the popular project "Humans of New York," denounced Donald Trump as "hateful" in an open letter on Monday, charging the Republican primary front-runner with seizing on racial division and religious prejudice to advance his campaign.

"I've watched you retweet racist images. I've watched you retweet racist lies. I've watched you take 48 hours to disavow white supremacy. I've watched you joyfully encourage violence, and promise to 'pay the legal fees' of those who commit violence on your behalf," Stanton said, explaining why he chose to go public with his concerns despite trying "my hardest not to be political."

The Trump campaign did not immediately respond to a request to comment.

Stanton began "Humans of New York," an online compilation of viral photographs and personal interviews with city dwellers begun, in 2010. Three years later, he cataloged his work in a New York Times bestselling book.

In 2015, Stanton traveled to Turkey and Jordan, where he met with a series of refugee families as they sought to leave the region for the United States.

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