The response, as one might expect, is not much of one, simply telling the fans that they appreciate the affection for the shows and to enjoy the episodes they've got left.
"Thank you to all our fans for expressing just how much they love DC Nation on Cartoon Network," DC wrote to their official Facebook page. "There's still more new Young Justice and Green Lantern: The Animated Series to enjoy in the coming weeks. And DC Nation isn't going anywhere; There will be plenty of new adventures coming your way later this year."
As you might expect, this hasn't been received as much of an answer; most of the commenters are still just lamenting the losses of the shows, with one commenter responding succinctly to DC's statement: "I think they are expressing how much they love the shows you are cancelling not DC Nation itself," fan Adam Tasker said.