Do you think that he wouldn't have resigned if he had read the piece beforehand? Would that have changed their decision to publish? They also demoted the editor who did the actual editing. It doesn't seem like it's obviously journalistic malpractice to publish bad and wrong opinions that come from US Senators, even if the opinions are very bad and wrong. The objection to the piece was to its contents, something the editor has finite control over if they're going to publish at all.
Certainly it's debatable whether that piece should have been published, but the stories about failures of professionalism sound like reasons they came up with after they published something that plenty of other major newspapers would have published, and discovered that their readership and employees really didn't like it.
To be clear, I think it's totally fine that the organization runs that way, but I think it's wrong to put them on a pedestal.