We ALL can have a bad day, even an actor who feels challenged by a reporter. I am sure Clooney is defensive about the movie because it did poorly at the box office in America and he put a lot of himself into it.
Besides, doesn't a reporter lose his journalism cloak when he says "I found your movie boring", as opposed to sharing some other person's review of the movie and then inviting Clooney's comment?
When asked about the poor quality of one of HIS movies, I understand actor Michael Caine once smiled and said that he had a very high lifestyle that is well maintained by a low grade of movie. I prefer Clooney's honest (albeit overly defensive and emotional) reaction to Caine's smug quip, don't you?
Just my two cents.