"Harry Potter" author JK Rowling fired back at liberal comedian John Oliver for defending transgender athletes in women's sports, telling him to "read the room."

After Oliver dedicated an episode of 'Last Week Tonight' to the right's “obsession” with trans athletes, Rowling disparaged the late night host, calling him a “sellout.”

J.K. Rowling and John Oliver are facing off again over the issue of transgender athletes. The duo, linked by their respective creative partnerships with HBO, clashed last November after Oliver argued that there was “no evidence” trans athletes “pose any threat to safety or fairness.