I wonder if my correspondent has in mind any household names here. Once again, Ammon Shea has been rifling through the Oxford English Dictionary in search of an apt word.
 
Will Martin, of Charlottesville, VA, writes: "I've long sought a word to describe the intersection of 'insensitive' and 'innocent' to describe the actions of those among us who are simply too shallow or immature to deserve the shade of malice implied by 'insensitive,' yet too foreseeably destructive in their actions to deserve the kindness implied by 'innocent.'"

Ammon Shea replies: "Although the first word that springs to mind is teen-aged, I'm also rather partial to the word incogitant, as it has two meanings - 1. inconsiderate, and 2. not having the faculty of thinking - that I think almost cover the concept you refer to.

"Since I do not have a perfect match for this, I will also offer up airling, which, as a noun, does come fairly close to what I think you are looking for.  It describes someone who is young and thoughtless."