J.K. Rowling has turned on John Oliver over the issue of transgender athletes in women’s sports.

The Harry Potter author accused the host of HBO‘s Last Week Tonight of being happy to see women suffer sporting humiliation in support of an “elitist post-modern ideology.”

Rowling’s attack on Oliver comes after the comedian defended the right of transgender women to compete in female sports at high school.

Speaking on his HBO show last week, Oliver argued that there are “vanishingly few trans girls” competing in schools and there is “no evidence they pose any threat to safety or fairness.”

In a lengthy post on X (formerly Twitter), Rowling said Oliver was an “undoubtedly intelligent person [who] spouts absolute bulls**t to support something he wants to be true, but isn’t.”

Rowling said she was reluctant to attack Oliver because he gave time to her charity, Lumos, and she “liked him very much” when they met. “Nothing about this feels good,” she added.

The argument is also awkward for Warner Bros. Discovery, given Rowling and Oliver are effectively colleagues. Rowling is heavily involved in adapting Harry Potter into a television series for HBO, which doubles as the home for Last Week Tonight With John Oliver.

She argued Oliver was “happy to watch females suffer injury, humiliation and the loss of sporting opportunities to bolster an elitist post-modern ideology embraced by a minute fraction of the world’s population.”

She continued: “Again and again I’ve come up against men who argue exactly what Oliver does here, using the very same talking points. With a straight face, the ‘believe the science’ guys will say ‘actually, we don’t yet have enough data to say whether men and boys are stronger and faster than women and girls’. The ‘be kind’ crew can’t see what the issue is. ‘Why are you bothered, it only affects a tiny minority of females?’

“They’ll stare unabashedly into a camera and insist that their audiences’ eyeballs are incapable of seeing what’s plain as day, and that there’s something wrong with the great unwashed for believing that girls are being robbed of opportunities and put at physical risk.”