The vast majority of news is intended to convince the public that something noteworthy has occurred. Occasionally, an event or opinion that is contrary to the political slant of a media organisation will become popular enough to demand coverage. Begrudgingly, the event will be reported, but rather than produce an objective analysis, those disseminating the news will attempt to foster skepticism within the audience.
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The BBC News website prolifically uses quotation marks for this purpose. An example is today's headline: Kurdish Rebels `begin leaving Turkey'. There isn't a quote that includes those words within the article, meaning the purpose of the irregular punctuation is to foster skepticism. You're supposed to ask if they're really leaving Turkey, and why they might lie about leaving.
On TV news, the same objective is achieved when newsreaders, correspondents, and contributors alter the tone of their voice. You will often hear a news anchor raise the pitch of their voice in an incredulous way. The subtext is "I don't believe this and neither should you". This is an extremely common method for inserting the opinion of a media organisation into news that is supposed to be factual.