In fact, even in less respectable newspapers this is generally true. I worked at a less respectable newspaper for several years; whenever I wandered into the editorial area I was treated as being slightly below toenail clippings in the order of creation.

It's best to think of a newspaper as a device that multiplexes two totally independent feeds. One feed is ads and classifieds, the other is editorial material.

Conspiracy theories to the contrary are just embarrassing. Really. Journalists are tremendously and fiercely proud of themselves (to a fault). Suggesting to a journalist at a serious newspaper that their writing is biased based on what the display department did last week is going to get a mix of reactions from laughter to a punch on the nose for uttering such inflammatory fighting words.