I would be interested to learn your thoughts on how bias is objectively defined.
Are you interested in how I define bias? Or, rather, are you interested in how objectivity vs bias can be identified?
Definition is easy. The relevant dictionary definition is:
"A preference or an inclination, especially one that inhibits impartial judgment."
Their definition is close enough that I could accept it all on its own, but I might also fine tune it to add a connotation that bias tends to refer more to
political preferences and inclinations.
How would you recognize bias in any given news report? That's less easy, but still not particularly hard. Do the reporters tend to favor facts, ideas, or contexts that fit in with their own political inclinations? Do they tend to ignore or downplay or try to dispute things that is disagreeable to their own politics?
As relates to NPR and their specific story on AKs, it's pretty clear that they run with a strong bias against the guns, against their private ownership and use, and by inference, against the wider concepts of RKBA. We've covered this already in the thread.
An independent or unbiased story might be an overall accounting the design, history, and use of the AK throughout the world, or it's history and use specifically within the US. But it's critical not to cherry pick which elements related to the AK you present and leave out, as NPR apparently did in their story.