"In 2015, I was the founder of Black Lives Matter in St. Paul," said Rashad Turner, who now leads the pro-school choice group Minnesota Parent Union.
"I believed the organization stood for exactly what the name implies – Black lives do matter. However, after a year on the inside, I learned they had little concern for rebuilding Black families," he added.
Turner's video, published to YouTube last week, highlighted how the group's website stated that it wanted to "disrupt the nuclear family structure."
"And they cared even less," Turner added, "about improving the quality of education for students in Minneapolis. That was made clear when they publicly denounced charter schools alongside the teachers' union."
"I was an insider in Black Lives Matter and I learned the ugly truth – the moratorium on charter schools does not support rebuilding the Black family. But it does create barriers to a better education for Black children."
BLM did not respond to Fox News' request for comment.
Turner's comments touched on an ongoing criticism of BLM – namely that its goals and political positions are much more left-wing than the name might suggest.
The group has acquired heightened popularity in the wake of prominent police encounters that sparked ongoing protests in recent years. Politicians and other leading figures have adopted the slogan as well.
Recent events, however, have intensified scrutiny of its leader and her ideas. Co-founder Patrisse Cullors came under fire after it was revealed she bought four homes for more than $3 million. The self-described "Marxist" was also seen in a resurfaced video favorably comparing a book to the "Little Red Book" propagated under Chinese dictator Mao Zedong.
The BLM curriculum also engendered controversy over ideas the organization was promoting in schools.
She told the Associated Press on Thursday that she was leaving the position to focus on other projects, including the release of her second book and a television deal with Warner Bros. She held the top post at Black Lives Matter Global Network Foundation for more than five years.
The activist said she had created "the necessary bones and foundation" at the organization and felt the "time is right" to leave. She asserted that her exit was planned for more than a year and was unrelated to scrutiny regarding her personal finances. "Those were right-wing attacks that tried to discredit my character, and I don’t operate off of what the right thinks of me," Cullors said.
Fox News' Thomas Barrabi contributed to this report.