They’re demonized because they’re an awful regime that horribly oppresses their own people.
Of all the reasons to demonize a government, that seems like a pretty good one. Why the snark?
Whatever NK does seems relatively tame in today's world. On the global stage it's generally thought of as a larger crime to oppress the peoples of other's countries (either the ukraine or iran conflict should fit your priors).
I would be less snarky if the faux concern didn’t just last as long as the media tells you to. Most recently, there was a period where Myanmar and the Uyghurs were in vogue, but not anymore. NK is more evergreen it seems.
Setting aside the genocide, it is particularly funny at a time when Western governments are oppressing their own by crushing dissent on Israel, but I don’t see the same outrage there.