The Guardian? I´m sorry. but after Snowden leaks it seem The Guardian was taken under control of MI5/6.Most sources are free but very few sources on the internet aim to be unbiased. Being human we like to go to sources that reinforce our beliefs. Right wing Americans might watch Fox News while UK citizens on the left might read The Guardian. I suspect that's why people always seem so polarised these days.
Anyone can spend time to add information into wikipedia. Some people will add bad information - that's just the nature of people. If an editor looks at your change and finds it wrong or wildly biased then it only takes a moment for them to revert your changes. I suspect those that dislike Wikipedia are those that have had their edits removed by editors.
and editors "control" edits based and enforcing on their own biases. And for many years now Wikipedia has become just an additional tool of information warfare, historiography and bias, and a lot of control on the part of some entities with short acronyms.