Washington (CNN) Organizers behind the Women's Convention still feel the Bern -- and for that, they are feeling the backlash.

On Thursday, the Women's Convention organizers -- who also led the Women's March in January -- announced Vermont Sen. Bernie Sanders will be a featured speaker at the three-day event, which will take place in Detroit later this month.

The convention "aims to have participants leave inspired and motivated, with new connections, skills and strategies for working towards collective liberation for women of all races, ethnicities, ages, abilities, sexual identities, gender expressions, immigration statuses, religious faiths, and economic statuses," according to its press release.

The news of Sanders as one of the headliners was met by mixed reactions on Twitter.

"What ultimately disappoints me about the choice of Sanders to open the first Women's Convention in some 40 or so years is that we have some excellent leaders to choose from who are women," Valerie Street, who tweeted her disappointment, told CNN. "Ones who are blazing their own trails in American politics right now."

The 35-year-old, who is a community organizer from Austin, Texas, said she is not planning on attending the convention because of scheduling conflicts; though she did participate in the March in January.

"The Women's March nucleus has been such a woman-led movement," she said. But the Sanders news "seems like an odd departure from that at a critical time."

Others echoed this view, and questioned why a man is the opening-night speaker. The convention's official theme is "Reclaiming Our Time," inspired by the viral phrase Rep. Maxine Waters' repeated to Treasury Secretary Steven Mnuchin in August. Waters will also speak at the convention.

Sorry. I'm not attending a women's convention where the opening night speaker isn't a woman. Perhaps consider these choices next time. pic.twitter.com/HiVpQ3I78n — Jean Grey 2017 (@JeanGrey80) October 12, 2017

"Sorry. I'm not attending a women's convention where the opening night speaker isn't a woman," one Twitter user wrote, sharing a photo collage of Sens. Elizabeth Warren, Kamala Harris and Amy Klobuchar. "Perhaps consider these choices next time."

The petition, created by Amanda Hambrick Ashcraft, said: "Bernie's voice, and the voices of ALL men, women, non-conforming, non-binary, cis, and transgender people who share a passion for the unity principles of the Women's March are needed and necessary voices for this movement. We want them at the convention. We want them listening. We want them leading. We want to learn from them, be challenged by them, changed and ignited by them. We even want them speaking at the Convention -- just not opening it. ... Having a man's face only continues the invisible presence, work and voices of women."

Some of the backlash geared toward the Sanders pick also stems from leftover frustration from the 2016 election. Although the Women's March rallied thousands across the US, some argued the organizers were not inclusive enough of Hillary Clinton, who was the first woman to win the nomination for president of a major political party.

"I knew you weren't to be trusted when you threw HRC under the bus at the march, but this is beyond the pale," one user wrote on Twitter Thursday.

I knew you weren't to be trusted when you threw HRC under the bus at the march, but this is beyond the pale. — RogueArtist (@TinaDuryea) October 12, 2017

Despite the uproar, Tamika Mallory, Women's March co-president, said she feels Sanders is the perfect fit for the convention, describing him in a statement as a "fierce champion of women's rights" and someone who has bolstered "female voices throughout his career of public service."

"We invited many elected officials to our convention that align with the purpose and mission of our existence -- to harness the political power of diverse women and their communities to create transformative social change," she said in follow-up statement after the news was announced. "We are thrilled that Rep. Maxine Waters and Sen. Sanders will be speaking at the Women's Convention."

Mallory elaborated that while some female lawmakers won't be present, they still extended their support for the event.

"We all know how busy women leaders are, and we are grateful for the support of women like Secretary Clinton along with Sens. Harris, Warren and (Kirsten) Gillibrand," Mallory said. "Although their schedules did not allow them to join us in Detroit the weekend of October 27, they will be fighting for our shared values, as they do every day. Our program features more than 60 women leading in activism, organizing and advocacy, as well as grassroots leaders running for and serving in office across the country. We are excited to come together, to unite across our differences and to fight for the future we all believe in."

In a series of tweets on Thursday afternoon , Mallory addressed criticism from Women's March followers.

".@womensmarch is led by women, mainly WOC. We announce one man as a speaker among over 60, and y'all start saying he's our leader?!" she wrote. "When you lash out at WOC leaders, saying we have a man as our headliner/leader, you erase our work. You erase Rep Waters' work. LISTEN TO US. To the folks yelling at @womensmarch & directly at me: Why does your version of advocating for women's rights = bashing Black women leaders?"

.@womensmarch is led by women, mainly WOC. We announce one man as a speaker among over 60, and y'all start saying he's our leader?! — Tamika D. Mallory (@TamikaDMallory) October 12, 2017

She pointed out that the convention has over "60 speakers currently lined up. Only 2 are men." She emphasized that Waters, who is a black woman, was announced as a speaker in mid-September.

A representative for Sanders said he had no further comment aside from his additional statement in the press release, in which he expressed his enthuasism for the event.

In a statement provided in the initial press release, Sanders expressed enthusiasm about the event.

"I'm honored to join the women at the front lines of our struggle for economic, social, racial and environmental justice," Sanders said. "In January, millions of women came out in an extraordinary and unprecedented display of power and resistance. Now more than ever, we must support the leadership of women across the country and fight together to advance our progressive agenda."

Other speakers include actress and activist Piper Perabo, political commentator and community organizer Sally Kohn, The Young Turks reporter Nomiki Konst, co-executive director of the Indivisible Project Leah Greenberg, Michigan Democratic gubernatorial candidate Gretchen Whitmer, Michigan state Rep. Stephanie Chang, Georgia gubernatorial candidate Stacey Abrams and others.