(CNN) By pledging his allegiance to ISIS during his deadly attack, the Florida gunman tied himself to more than just radical terrorists. Omar Mateen joined ranks with a group that has been relentless and brutal in its persecution of those perceived to deviate from mainstream sexuality.

People tortured. Gunned down by firing squads. Beheaded. Burned and stoned to death. According to eyewitnesses and video, this is the fate of many gay people in the lands of ISIS, where they are routinely hunted and murdered because of their sexuality.

At the U.N. Security Council's first-ever briefing on LGBT issues around the world last August, an Iraqi man with a disguised identity testified, "In my society, being gay means death."

He added, when ISIS "kills gays most people are happy because they think we are evil." He went on to describe how ISIS uses phone and Facebook contacts of suspected gays to find others and track them down. "And it is like dominoes," he said, "if one goes the others will be taken down, too."

Gay men hurled from buildings

Read More