Even if you want to focus on an ethical argument I'm not sure how to create a standard to compare them. Who is worse, Fox News who wears their bias on their sleeve or the New York Times who constantly hold themselves out as remarkable while piping all kinds of military and intelligence propaganda through to their readers. Who is worse? The organization that just outright supported Bush or the one that claimed to be a check and then held the illegal NSA spying story through an election?
IMO it's best not to choose which is better or worse. It's better to know how to read through both.
Another interesting point you brought up: how long a go should we look? Is today’s NYT still culpable for mistakes made nearly 20 years ago? (Not defending them, as I’m sure there are more recent examples. But when has enough time passed?)
I might report that "a woman is suing McDonalds for spilling hot coffee on herself". That is an unbiased fact. And it implants a story of runaway litigiousness. If I also report that "McDonalds was warned many times about the temperature of its coffee and even sure once already and the woman sustained 3rd degree burns" the story becomes one of corporate malfeasance.
Compound this further. I now state that the woman won millions of dollars, you may be tilting back toward over litigiousness. But if I report that she only sought damages and the jury awarded her punitive damages of its own accord the we're back to corporate malfeasance.