Bad journalists are biased. Good journalists will present a story as factually as possible and as void of bias as possible (of course it's impossible to not have any biases). Opinion pieces can have as much bias as they like as long as they're strictly marked as opinions.
That's not true. Any journalist would tell you that picking the stories you chose to cover is just as much a bias as how you chose to cover them. Even then, the specific words you pick, how you ask the interviewees, how you place the story on the page, what you pick as the "related stories". All of that is Editorial and reflects an opinion.
Good journalists are open about their angle. Bad journalists tell you they are "unbiased" and "just bringing you the facts".