There is media and there is media. Obviously, some media, (ads being the most obvious) do seek to alter behaviour. I am far from convinced that "media" influences people to the degree that some like to hide behind. I think they reflect it, politically anyrate.
Bold bit is spot on. The news media exists to sell itself. It reports on what people will read. It shapes editorially, but no matter what the editor does if there's no appetite to read it then it falls on its' backside.
Corbynism relies on being the victim. They need to have that all-encompassing evil entity to blame for their warped view of the world being the minority. The media are a convenient scapegoat - see the treatment of Kuenssberg for details.