Ugh, The Guardian is not a good media outlet. Where the Daily Mail in the UK is an awful right wing biased and often incorrect news source, the Guardian is just the same but Left instead of right.
They use the same tabloid style unsubstantiated personal hit pieces twinned with scaremongering opinion pieces. Never use them as a source for anything.
They really aren't that bad, and nowhere near the levels of the Daily Mail when it comes to using factual and properly sourced information (of which I'm not sure the Daily Mail even bother with). The Guardian have a definite left wing bias and have a strong tendency towards emotionally charged words but their investigative pieces tend to be well researched and they'll generally use factually correct and sourced information.
There are a lot worse publications out there.