After finishing up a panel that brought together members of Congress and the Parents for Transgender Equality National Council on Wednesday, prominent trans advocate Sarah McBride sat in a room in D.C.’s historic Cannon House Office Building where she was sorting through pictures with an event photographer.

McBride, the press secretary for national LGBTQ advocacy group Human Rights Campaign, is perhaps best known for being the first transgender person to address a major political party’s national convention. She, along with other HRC staffers, were on Capitol Hill to advocate for passage of The Equality Act, a proposed bill that would add sexual orientation and gender identity to existing federal civil rights law. The bill is a top legislative priority of the Democratic-controlled House.

Just outside the room where McBride was working, stood Kellie-Jay Keen-Minshull, an anti-trans activist from the U.K. who goes by the pseudonym “Posie Parker.” Keen-Minshull started a Facebook Live broadcast, walked into the room where McBride was sorting through photos and proceeded to aggressively confront her, intentionally misgendering her multiple times.

“Why don’t you care about lesbian girls at 14 getting double mastectomies? Why don’t you care about that Sarah?” asked Keen-Minshull, who often refers to transgender men as “lesbians.”

During the broadcast, which appears to have been deleted from Facebook, Keen-Minshull and her associate, Julia Long, can be heard accusing McBride of “championing the rights of men to access women in women’s prison,” not caring “about lesbian girls” and hating lesbians.

As the live broadcast finished, Keen-Minshull said, “Everyone, this is Sarah McBride ignoring women and girls’ concerns as usual — so typically male!”

The Human Rights Campaign and several other LGBTQ advocacy groups were quick to condemn the incident.

"That the targeted harassment occurred following a moving meeting between parents of trans kids and members of Congress reinforces the massive gap between our message of love and their agenda of bigotry,” Olivia Dalton, an HRC spokesperson, told NBC News. “No one advocating for their basic human rights should face such hate and hostility.”

The incident also generated backlash online, with lawmakers, celebrities and LGBTQ community leaders coming to McBride’s defense.

What happened to @SarahEMcBride after yesterday's event was disgusting and unfair. We support ALL members of our #LGBTQ family. I respect her strength in not responding to hate. I attended the event beforehand - was very positive. #StandwithSarah https://t.co/EPnHCaBEdZ — Sean Patrick Maloney (@RepSeanMaloney) January 31, 2019

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So sorry this happened to you Sarah. Thank you for foregrounding the vital, life saving work of valuing the lives of trans people especially trans children. #TransIsBeautiful #WeWontBeErased https://t.co/agLUtXWRG0 — Laverne Cox (@Lavernecox) January 30, 2019

My friend @SarahEMcBride is an amazing woman, trailblazer and genuinely decent person.

She's dedicated her life to equality and equity, persevering over hate and with the infinite grief of losing her husband, all to make our world a better place.

I adore her and her resilience. https://t.co/jyIfIj44a0 — Danica Roem (@pwcdanica) January 30, 2019

STRANGE BEDFELLOWS

HRC put the blame for Wednesday’s episode not just on U.K. residents Keen-Minshull and Long, but also on U.S.-based conservative think tank Heritage Foundation.

"It is disturbing but not at all surprising that anti-transgender extremists brought to the United States at the behest of the Heritage Foundation would stoop to harassing a transgender woman and parents of transgender youth," Dalton said. “Shame on the Heritage Foundation for fostering this kind of atmosphere.”

A spokesperson from the Heritage Foundation said the organization had “nothing to do with” Keen-Minshull and Long being in the U.S. and had "no contact with them before or after our Jan. 28 event, and have zero connection to anything they did afterward."

The Heritage Foundation, which has long advocated against LGBTQ rights, has not been shy about its opposition to transgender rights, and it has previously joined forces with so-called radical feminists who share very little in common with the organization aside from anti-transgender views.

In fact, earlier this week, the Heritage Foundation hosted a panel in D.C. titled “The Inequality of the Equality Act: Concerns From the Left.” The moderator, Heritage Foundation’s Ryan T. Anderson, and the four “radical feminist” panelists “from the left” seemed to just have one thing in common: opposition to trans rights.

“If gender identity becomes a protected class in federal civil rights law, there will be serious negative consequences,” Anderson said in his introduction. The increase in those identifying as transgender, he added, “has become an epidemic.”

Keen-Minshull, who attended the Monday panel, posted a Facebook Live video from inside the Heritage Foundation’s headquarters praising the conservative group for being the only organization that would publicize the dangers of transgender rights.

“Nobody else would do it,” Keen-Minshull said in the teary-eyed video, sharing stories of mothers who have “lost” their children to the transgender “cult.”

In an interview published Thursday in U.K. magazine Spectator, Keen-Minshull claimed the U.S. exported the concept of transgender rights to the U.K., “so to stem the flow of female erasure we have to come to its source.”

Keen-Minshull’s anti-transgender views have already gotten her banned from several social media platforms, and she is infamous in Britain as the activist behind a seemingly innocuous billboard campaign that has been criticized as transphobic. Keen-Minshull and her organization, Standing for Women, advocate for a discreet, definable political goal: the right to segregate transgender women and cisgender (non-transgender) women in female-only spaces, like bathrooms and locker rooms.

While the civil rights group Southern Poverty Law Center has previously noted that socially conservative groups were implementing a “divide and conquer” strategy to “separate the T from LGB” (several self-proclaimed radical feminists that have collaborated with Heritage Foundation identify as lesbians), a prominent LGBTQ advocate described this as a “hopeless strategy” in the U.S., because the right-wing movement in the U.S. is built on “Christian evangelicalism" that is opposes both transgender and gay rights.

The result, according to the advocate, who asked their name not be shared for fear of being subjected to harassment, is that “the organized elements who are anti-trans are also the organized elements that are anti-gay, and anti-choice, and in many cases the same folks who are anti-immigrant.”

“Our bullies,” the advocate added, “they’re the same people, so there’s that sort of visual, very clear tangible recognition that anti-trans prejudice is inexplicably linked” to other forms of prejudice.

NOT AN ISOLATED INCIDENT

The clash between so-called transgender-exclusionary radical feminists (sometimes referred to as TERFs) and transgender advocates is not limited to this week’s events. In fact, the issue appears to have boiled into public view over the past year or so.

An anti-transgender activist group called “Get The L Out” protested at last year’s pride march in London, arguing that lesbians must leave the LGBTQ community in order to prevent trans people from entering their spaces. After the event, the organizers of the London pride march apologized and said the "actions of eight people did not stop the joy and love,” according to the BBC.

As previously reported by NBC News, multiple editors and publishers from prominent English-language lesbian publications around the world wrote a joint letter in December titled “Not in our name” decrying anti-trans bigotry within the lesbian and feminist communities.

“DIVA, Curve, Autostraddle, LOTL, Tagg, Lez Spread The Word, DapperQ and GO Magazine believe that trans women are women and that trans people belong in our community,” the statement reads. “We do not think supporting trans women erases our lesbian identities; rather we are enriched by trans friends and lovers, parents, children, colleagues and siblings.”

The growing tensions between trans-exclusionary feminists and trans advocates comes as both the U.S. and the U.K. seek to add transgender protections to existing civil rights laws. In the U.K., the Conservative government is pursuing changes to the Gender Recognition Act that would make it easier — and less medicalized — for trans people to change their gender on documentation. In the U.S., the Equality Act is poised to be reintroduced in the House of Representatives as early as this month.

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