If they're all remembering Harvey Dent, then they're still remembering the era where he was most brave; standing up against the Joker, the guy who mutilated his face and killed his girlfriend. 
When the Dent cover up comes out, how does Joker's name get completely omitted from that whole debacle when he was the one who corrupted Dent and he's the reason why Batman burdened himself with Dent's crimes; "The Joker cannot win".
I don't understand and never will why a mention of Joker's name would be bad for Heath's memory, or be out of context in this movie when the character's actions are still having consequences on the characters and events in this movie.
The official synopsis was Bruce is still recovering from the physical and mental trauma of his encounters with Joker and Dent in TDK.
http://www.unleashthefanboy.com/movies/more-from-the-cast-of-the-dark-knight-rises/8012