The US does openly employ people to do this. One article about it: http://www.wired.com/2012/07/counterterrorism-trolls/all/
> Within the State Department, a Silicon Valley veteran has quietly launched an improbable new initiative to annoy, frustrate and humiliate denizens of online extremist forums.
Not exactly the comment section of BBC, is it?
http://www.linuxjournal.com/content/nsa-linux-journal-extrem...