When the Women’s Convention announced that Bernie Sanders would speak on the opening night of its national conference in Detroit later this month, the response on social media was swift and brutal.

Many supporters of the group, which spearheaded the record-setting marches around the U.S. to protest President Donald Trump’s inauguration in January, were outraged that conference organizers would pick a white man to address a convention meant to elevate women of color. Others were annoyed that Sanders—who recently endorsed a candidate for mayor in Nebraska who has been criticized as anti-abortion—would be embraced by a movement that supports reproductive rights. Others nursed a grudge against Sanders and his supporters for their role in Hillary Clinton’s election defeat.

On the surface, the hoopla may seem silly: many of the critics were objecting to the misperception that the Vermont Senator was “headlining” a women’s conference. He isn’t. The Women’s Convention doesn’t technically have a headliner, but its featured speaker is Rep. Maxine Waters, a California Democrat who has called for Trump’s impeachment. Sanders is one of only two men among the 42 speakers at the three-day conference, held in Detroit from Oct. 27 to Oct. 29. The publicity around the former presidential candidate’s appearance was a function of the fact that he is the most famous speaker on the docket.

But the controversy over Sanders’s role in the Women’s Convention raises larger questions about whether the progressive grassroots uprising against Trump’s agenda can thrive as a “leaderless” movement that aspires to unite coalitions across the left.

How can the movement amplify the voices of specific groups—especially women, immigrants, and people of color—while embracing white men as full participants? How can it harness the activist outrage that drove the largest demonstration in U.S. history while expanding its ranks to win seats in the midterm elections? The best way for the so-called Resistance to achieve tangible change is to build a broad coalition. But is it still a women’s movement if it showcases male leaders?

In their first interview since the controversy erupted Thursday, the leaders of the convention defended the move, chalked up the controversy to a misunderstanding and expressed dismay that Waters’ role at the gathering was overlooked.

“Why did the same people not take as much interest in sharing and helping to uplift Maxine Waters and the other women of color?” asks Tamika Mallory, a racial justice organizer and co-founder of the Women’s March. “People who claim to be feminists often ignore the voices of women of color and particularly black women.”

Mallory acknowledged that inviting Sanders was a controversial choice. “Some people just don’t want to hear from Bernie Sanders,” says Mallory. “There are some people who don’t believe that a man has a place at a women’s convention.”

Bob Bland, an entrepreneur and Women’s March co-founder, said she was surprised by the controversy about Sanders’ role at the convention, which will include panels on mobilization for the midterms and activist training. “Do we want to re-litigate the past or move forward together?” asks Bland. “Even though we don’t agree on every issue, we have to work together to win the midterms in 2018. Otherwise we will continue to lose. We need to focus on that.”

Others disagreed. “This choice sends the wrong message,” tweeted Stephanie Schriock, president of Emily’s List, a political organization that funds and supports pro-choice women candidates, who is also scheduled to speak at the event. “We have more women leaders in elected office than ever before. Women ARE leading in the Senate. This is a moment to highlight them.”

A Change.org petition asking the Women’s Convention organizers to reconsider Sanders’s role had gotten nearly 8,000 signatures by Friday afternoon. The organizers also invited leading female Democrats like Clinton, Sen. Kamala Harris, Sen. Kirsten Gillibrand and Sen. Elizabeth Warren to speak at the Convention, but organizers say the event did not work with their schedules.

The dispute boils down to a question of strategy. “If the goal among the organizers is to try and generate the broadest possible support for their agenda, then it could potentially be the right call” to invite Sanders, says Jennifer Lawless, director of the Women & Politics institute at American University, who points out that Sanders has made feminist enemies when he advocated for endorsing candidates who oppose abortion rights. “If your goal is feminist ideological purity, it raises a lot of questions and suggests they might be selling out.”

The misunderstanding may have been rooted in the group’s aversion to hierarchy. The Women’s Convention is called “Reclaiming Our Time,” after Waters’s now famous retort that she was “reclaiming my time” in a congressional hearing. Waters is giving a major speech at the event on Saturday, but she is not given top billing on the agenda because organizers have so far avoided designating any keynote speakers or official headliners. Instead the speakers are listed in alphabetical order, and there is nothing on the website that indicates that any speeches are more important than any others.

“I was surprised that a lot of women that marched on January 21st were so up in arms over this,” adds Bland. “I wish that many had mobilized with us when we were marching to confront white supremacy in August.”

But that doesn’t mean the controversy is going away. “It highlights some of the deep issues that came out as a result of the campaign,” says Debbie Walsh, director of the Center for American Women and Politics at Rutgers University. “It feels a bit like the marginalizing of women at an event that is supposed to be put on by women, for women, about women.”

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Write to Charlotte Alter at charlotte.alter@time.com.