John Oliver
John Oliver did what he does best, mocking CNN over its coverage of what they claimed was an ISIS flag at a London Pride parade. The flag turned out to be one celebrating sex toys. Getty Unages

John Oliver started "Last Week Tonight" Sunday with the biggest news of the weekend: #LoveWins and the Supreme Court of the United States' decision to legalize gay marriage across the U.S. But it wasn’t long before he turned to mocking the media -- namely CNN’s misguided declaration that an ISIS flag was flying over the London Pride Parade.

Over the weekend, a CNN producer reported a black-and-white flag ISIS flag was being flown during London’s Pride Parade. Other outlets mocked CNN’s “exclusive” report that turned out not to be an ISIS flag, but rather a flag covered with silhouettes of sex toys.

In CNN’s defense, the flag was black and seemed to be a parody of the ISIS flag. Despite the backlash -- and devoting significant time to the report -- the network didn’t offer a correction, Oliver noted.

CNN’s reputation hasn’t yet fallen to that of Fox News, which is regularly mocked for inaccurate news reports. Still, CNN has weathered a fair amount of criticism over sensationalized news, such as the missing Malaysian Airlines flight and the Ebola outbreak.

Later in the episode, Oliver schooled the media at large over its treatment of transgender individuals.