It is not a democracy. If you want to shout your opinions from the rooftops you are perfectly entitled to set up your own forum to do so. STW is under no obligation to provide a platform for you
For democracy to exist, people need to be able to express and hear or read facts and opinions, especially so if they are controversial or contentious, and equally they need to be able to hear or read challenges of those facts and opinions. Any business or organisation that is part of – or facilitates – such public debate, such the media, the BBC, Facebook, Twitter, and yes even STW, has a public and moral duty to protect free speech. STW has already taken a stance on the Daily Mail, by refusing to allow direct links to its website, but it has been quite open and honest about this and its ethical reasons for doing so .
Thats not the point and its not censorships strictly anyway. Censorship would be somone else telling STW to take it down.
When the media, commentators and others are afraid to raise or confront difficult issues and question a prevailing orthodoxy, that is a far more effective and insidious form of censorship than any crude government instruction not to publish something.
For example, consider this BBC article on the attempted murder of a UK Athletics official:
http://www.bbc.co.uk/news/uk-england-birmingham-37439875
The article completely omits to explain that the attacker was a transwoman, and that the official was investigating an accusation that the attacker had not been eligible to compete as a woman when he won the English women’s fell running championship. These were matters of fact which were known to the BBC at the time it published the article, but it deliberately chose to suppress them. Only after conviction and sentencing did the truth come out:
http://www.bbc.co.uk/news/uk-england-birmingham-39266777
Edited to correct the first article linked.