Should this not fall under the "private company, do what they want" mantra we were all so fond of wrt (pre-Musk...) Twitter, Facebook, et al? The further advice then was; "make your own social media platform."
Same thing happened at LA times a few days ago, also replete with an editor quitting, when owner Patrick Soon-Shiong blocked the same Kamala endorsement.
You're free to not subscribe, some editor or other is free to quit, and owners are free to do as they please with their private property. Freedom. What a great idea.
It would seem you didn't care or notice because there previously wasn't an opinion conflict with the owners.
It's only bad when they refuse to bend to your political orthodoxy, not when they knowingly print dangerous and false stories about nation state hacks (eerily similar to NYT's lies about WMDs in Iraq) -- something likely to drag the world to war again.