I don't see what the man has to apologize for. Trump is a big boy, he can handle it.
He apologized for failing to adhere closely to his own, his employer's and general principles of rational analysis, inference and conclusion forming, not for demeaning Trump.
Reuters Breakingviews Editor Rob Cox admitted that he “responded emotionally and inappropriately” after being called out for jumping to conclusions prior to the facts emerging. [from the Reuters article]
Though my comments were entirely personal, they were not in keeping with the Reuters Trust Principles and my own
standards for letting facts, not snap judgments, guide my understanding.
--
Rob Cox
Adroit communicators and keen thinkers usually try to refrain from declaring things bereft of sound or cogent founding. Doing so is a matter of integrity and honesty. The communication problem comes when audience members infer from a speaker's/writer's remarks more or less than what the author actually stated and implied. Aptly and accurately interpreting another's communication requires one understand well not only the denotation of the words used, but also their connotations, as well as the meaning carried by punctuation, cadence, verb tense, verb mood and and grammatical structure.
Cox, as is the case with any rational person of integrity, is well aware of when they've uttered an irrational remark. He is right to be remorseful for expressing publicly
ideas founded emotionalism rather than rationality. Founding must be logical; however, optimally, appeals are emotional. Normative arguments that are fallacious don't hold water any more than do positive arguments that have no "heart and soul." Cox's now-deleted tweet was all "heart and soul" but fallacious, the latter being why he apologized.
As for why Reuters gives a damn, well, that's got everything to do with the news service considering Cox's tweet as having some sort of connection to Reuters. I presume the fact of his editorship
and his Twitter description of himself stating "Global Editor, Reuters Breakingviews. Tweets = Personal" is why Reuter's execs think his personal tweets reflect on them as well. Were he not to have mentioned Reuters in his description, I suspect the service wouldn't have had any concern over his tweet.