The singer and her bandmates released a joint statement on Friday, April 26, attacking their DJ pal for his decision to work with Brown on his new track "Light It Up".
They said: "We are really upset, confused and disappointed by Marshmello's choice to work with Tyga and Chris Brown. We like and respect Mello as a person but working with people who are predators and abusers enables, excuses and ultimately tacitly endorses that behaviour. That is not something we can or will stand behind."
Brown pleaded guilty to felony assault of Rihanna back in 2009, and he's the subject of an ongoing lawsuit over an alleged rape in Paris.
He responded by firing back at Mayberry and her bandmates, calling them "losers" and wishing they "walked in front of a speeding bus full of mental patients."
Lauren reiterated her band's stance onstage at the beginning of Chvrches' Fortress Festival in Texas on Saturday night (April 27), stating they feel it's "morally dubious" for musicians to work with artists who have a history of violence.
And she joked about threats from Brown's fans, telling the audience she was considering buying a "bullet proof tutu" to protect herself.
Marshmello, who introduced Chvrches onstage during his Coachella festival set in California earlier this month, dropped the music video for his new party anthem, featuring Brown and Tyga, on Thursday morning.