Good point about the judge't limited time with him, however, that's not the judges only knowledge of the defendant. Likely, he had read hundreds of pages of briefings, assessments and opinions of noted child / social workers, psychologists, case managers, etc. - and subsequently heard testimony from each as well - both those called on behalf of the prosecution and defense, alike.
While his time was limited, to be sure, it's not accurate to believe that this was the sole point of reference which was used in the formulation of his opinion.
Your comment about presuasive comments is also spot on, however, if a judge were truly afraid of being overturned on appeal, he would be most concerned with the use of prejudicial language that could most effectively substantiate a appellate claim on the grounds of judicial bias.
Simply, had the defendant's remorse been exampled in any way, supported by any evidence, or witnessed by any person, the judge would have avoided his chosen language at all costs. Obviously, he was confident in making such a strikingly unavoidable comment.
Please also notice that the case was, in fact, appealed......with the defense making no mention of the presiding judge exhibiting bias of any sort. Surely this would have been listed amongst their 20 some odd challenges, had they the faintest notion that such an accusation could be corraborated.
Your point was well taken, but the likliest reason for the judge to remark at his lack of remorse was due to the fact that the defendant had failed to exhibit it, and not for fear of being overturned by an appelate court.