Tell a kid who lost a parent that justice wasn't served. Tell the wife of a firefighter that went in after the planes hit that justice wasn't served.
There are those who deserve celebration. To them, and to all my friends serving to protect me in a way I wasn't willing to so myself, some sort of positivity is fair.
You can argue the symantics of the subject all you want, but to those people, in my opinion, that is indeed justice being served.
Not the loss of life of another person, but the things which that person represented.