Soliciting and editing opinion pieces was part of my job many times during my almost 50 years around the news and communications business. Being a highly opinionated sort myself, I enjoyed that work quite a lot.
However, I've often been unsure about just how much to pressure an op-ed writer to add to, better justify or delete something they wrote.
In the end, I generally left the final decision to the writer. An op-ed is, after all, the writer's opinion about a subject and what they think is most important about it. It's the writer's prerogative to cherry pick from among the "facts" available on whatever the issue. The editor's job is to edit for style, grammar, originality, organization, libel and slander, personal animus and logical cohesiveness.
It's true that this can -- and often does -- result in one-sided, unfair and even intellectually dishonest copy. But that's the nature of the beast. Don't like it? Well, if you're in a position of authority you can always decide not to publish a piece or solicit another writer to produce one more to your liking. Or you can write one yourself (and hopefully find someone willing to publish it, but that's another issue).
A recent New York Times op-ed about the soon-to-close Al Jazeera America is a case in point. (I'll get more precise shortly.)
One of the main reasons GetReligion was founded was to note this sort of imbalance when it shows up in basic, hard-news copy, specifically as it relates to religion news.