The position on this incident is very clear to me.
By attaining the title of "Captain" , the employer, and the certifying body has put certain authorities in his hands. They are saying he is responsible for making all kinds of judgements, that affect safety, among other things.
AND they , by giving this rank, are acknowledging that they are putting trust in his capabilities.
The employer has , in my opinion, every right, after the fact to discuss with the Captain, how he came to this decision and why.
They may, as in this case, disagree with his final decision .
But it is a dangerous precedent to dismiss a Captain for his decision without some compelling evidence of dereliction of duty.
Even if the case were a bad decision, to err on the side of safety, a post discussion of such would only be warranted . Unless a pattern over time is observed, one must assume that his decision was made in good faith, with the safety of his passengers a priority.
A Captain should not have to consider in his/her assessments of a a safety issue whether it will lead to a firing.
Imagine....."Hello Captain XYZ , yes you are the final authority for your airplane today, by the way if you make one decision that we dont like (read cost us money) we will fire you ,we do not care about your exemplary record, or anything else...what? of course we trust you to do the right thing ! "