The world of juried shows is indeed strange.
The job of the juror is to select a cohesive set of work. In that sense, I can understand why a juror might reject some work with little or no consideration based on the subject, or style, or technique, or even trivialities like the color or size of the frame. And frankly, it may be possible for the juror to make that decision without carefully studying the work. One of the challenges we have as artists is that we generally don't know what the juror is going to look for - even when we know who the juror is going to be (and in the vast majority of instances, that information is included in the Call), we don't know what kind of selection criteria will be applied. As a result, even though rejection is always painful, it may not mean that our work is not good.
So the thing that I find most upsetting about this instance is not with the juror, but rather with the gallery - they lied to Derek. To tell him that his work had been examined just as closely as the other submitted work and then rejected sent the message that the juror found his work to be inferior. Because that was not necessarily the case, it was unthinking and cruel.
But artists have to have rather thick skin to enable them to continue in spite of rejection. Rejection happens - for many reasons, some valid and some bogus. Deal with it.
I enter a couple of shows in our area each year, one of which is juried, and I've been fortunate to have work selected for the juried show in two of the three times I entered. And I have to agree with the juror that the piece that was rejected wasn't all that good - I almost didn't enter it. My greatest frustration, however, is not with the selection process, but rather with how the final show is hung. Its a mixed show, and it seems to me that the photography always ends up in a dimly-lit back corner.
On the other hand, I've also submitted work (on CD) in response to calls from other galleries. Rejection is one thing, but it really irritates me when they don't even have the courtesy to tell you that they aren't interested, and you simply get no response at all.