Editors have a lot of control over what is (and is not) published by a newspaper, so "the Guardian has a bone to pick with Julian Assange" could be translated to "the Guardian's editors have a bone to pick with Julian Assange". In addition, accuracy is not the only factor -- tone and angle are also incredibly important because they shape the conversation on a topic. And the tone of an article is definitely shaped by editors.
If there is a consistent record by a newspaper of negative (or in some cases outright false) articles about someone, I think it's fair to say that they have a bias against that person. I'm sure you'd agree with me the Fox News has a strong bias against AOC and Ilhan Omar -- it is sometimes reasonable to make a generalisation like that if the general trend is in a particular direction.
I don't think you can generalize editors so easily, either. They don't all operate on the same principles. Some exact more authority over tone than others. I don't know the Guardian's editors, so I can't speak to them.
I also can't speak to Fox News or American politics in that kind of detail.
Anyway this is going off of the main context of the thread, which was my original complaint. So if there's another one that comes up on this subject I think it would be more suitable to explore it there.
If there is a consistent record by a newspaper of negative (or in some cases outright false) articles about someone, I think it's fair to say that they have a bias against that person. I'm sure you'd agree with me the Fox News has a strong bias against AOC and Ilhan Omar -- it is sometimes reasonable to make a generalisation like that if the general trend is in a particular direction.