When you're a journalist who's part of a list of many journalists for an upcoming movie's 'press day', where stars and/or directors from the film talk about the plot, characters, inside stories, etc. (basically anything related to the film), you're usually expected to ask questions about the film and not the personal lives of the actors. And even if you do decide to walk that line, you better be careful. Any wrong question can mess things up.
Evidently, British Channel 4 journalist, Krishnan Guru-Murthy, did not get that memo. His interview of Robert Downey Jr. during the Avengers: Age of Ultron press day slot turned awkward when he stopped asking questions about the film and drifted towards Downey Jr's "dark history", his drug-filled phase and (the final nail on the coffin) his relationship with his father.
Where many others might have lashed out, RDJ chose to simply walk out.
Check it out. The awkward bit starts around the 5-minute mark.
Source - Channel 4 News