Man, is he annoying! But if you come back and talk to him one more time after you discover who the criminal is, he'll finally open up and tell you something of what's really going on with him. It explains why he is the way he is, why Niko was protecting him, and what he was shredding. You don't need to have this conversation to finish the game, but if you didn't, you might want to load in a saved game from before the endgame and talk to him, just for curiosity's sake.