Tharg, surely all opinion pieces are written to inform and hopefully influence your view on a subject. Your opinion can’t be controlled. I read very widely and am often influenced by what I read. I can as easily accept or reject the thinking of a writer in the Spectator as I can accept or reject the thinking of a writer in the New Statesman (both of which I subscribe to). Politically CapX is right wing and libertarian – it doesn’t hide the fact. It doesn’t make the articles it published any less valid. Writers and journalists get published where they can, it’s what pays the rent. The Editors of media such as CapX, the Daily Mail and the Guardian choose what to publish, not their rather remote financial backers.
You are quite right to be circumspect about the motives of anyone who tries to influence your thinking, but don’t focus on the media that carries the message. In the old adage, “don’t shoot the messenger because you don’t like the message”