I liked this story. I always knew that Connie Willis had a mean streak.
For myself, I don't think that the punishment had to be justified. This wasn't a morality play - it was a faerie tale. In faerie, bad things happen to people who kind of vaguely deserve it, usually because of fairly abstract violations like trespassing or breaking their word or being unkind and snappish to strangers and children...
Oh, yeah.
The moral is not that you deserve to die if you commit these minor infractions; the moral is that social niceties like property, integrity, and kindness are the grease that keeps the big iron machine of our world churning. If you let the machine get grimy, it breaks down, and... things... from the outside can get in. It's a metaphor for things like nature and the atavistic side of the human character, of course, but in stories, that metaphor is often realized as strange and inexplicable violations of the natural laws we know.
In other words, the lesson isn't "if you're a selfish jerk you're going to die and be trapped in a toystore forever." The lesson is "behave in a prosocial way or we're all going to starve together, you schmuck."