The Harry Potter creator, J.K. Rowling, and the performer known as Boy George have gotten into a nasty, more than week-long online spat over trans rights.

It started with Ms. Rowling’s June 6 post that said, “There is no ‘living as a woman.’ There is only living while being a woman, or performing a male idea of what a woman is, while being a man.”

“This is your obsession and it’s pretty relentless and for no reason,” the former Culture Club singer, whose real name is George O’Dowd, responded. “You are cruel JK.”

He ended the lengthy reply with: “Ladies & gentlemen and those of you still deciding. There are two type of people, nice people and c—s.”

In another post, Ms. Rowling posted about it being “very funny” watching trans activists try to distance themselves from a biological male who recorded himself in the women’s bathrooms at Disney World. Mr. O’Dowd responded, “Yeah, you get your fun from other people’s pain!”

The Harry Potter author later posted, “Which rights have been taken away from trans people?”

Another X user responded to her question by accusing her of persecution and Ms. Rowling anwered, “When ‘persecution’ is redefined to mean ‘not being allowed to reorganize society based on unfalsifiable feelings, to compel everyone else’s speech and belief and to take rights away from other protected groups’ you’ll be absolutely right.”

Mr. O’Dowd reacted to her post with: “The right to be left alone by a rich bored bully!” That’s when Ms. Rowling fully pounced at him.

“There are many differences between us, George, but some are particularly relevant to this debate,” Ms. Rowling stated. Then she noted that she is a woman and he is a man. Then she commented that he became wealthy and famous quite young while she struggled in poverty, and that is why she understands “the importance of single-sex spaces for women who’re reliant on state-funded services.”

Then she brought up Mr. O’Dowd’s 2009 sentencing after attacking a male escort. “I’ve never been given 15 months for handcuffing a man to a wall and beating him with a chain,” Ms. Rowling wrote. She said the overwhelming number of people who commit crimes of violence are males and that is why she doesn’t want men “identifying” into sensitive women’s spaces like domestic abuse and homeless shelters.

Ms. Rowling has been a vocal antagonist of the transgender community and advocate of so-called single sex spaces. She celebrated a recent ruling by Britain’s top court that only those people born female can be considered women.