You are right, though there are genuine bulk of information on the Internet but there are also many erroneous and fake information on it. It is full of unverify information and it's very important not to take everything on the Internet as the real thing
Even some websites got a fact checker, sometimes they're going with their agenda and don't do wholly their duty as a fact checker. That lies with their opinions and if the fact is against to what they believe, they'll flag it as a fake news or not genuine information.
And vice versa. It is one reason why there are a lot of people that don't believe quickly with such news that comes out from the medias, it has to be verified first.