Nightwing went through a pretty self-destructive phase after he allowed his arch enemy Blockbuster to be killed. He watched as the crime lord of Bludhaven got shot. So Dick does what he is unfortunately really good at: feeling sorry for himself and tells himself that he has failed Batman.
But after Dick almost got himself killed by overworking himself for six months, Batman drags him back to the Batcave so Alfred can look after his wounds. When Dick is awake, he expects Bruce to give him a lecture about his failure as a hero for not saving Blockbuster.
Well, Bruce IS pissed. But not because of that.
He is pissed at Dick for not taking care of himself and almost getting killed.
Batman is kind of a tough-love parent, but in a good way. He knows that Dick is blaming himself for Blockbuster’s fate, but he also won’t let Dick ruin himself because of it. He knows that Dick doesn’t need him to forgive him, Dick needs to forgive HIMSELF and move on from his mistake. Batman knows that Dick is a good man, too good to allow himself to drown in selfpity. And Dick shouldn’t expect Bruce to excuse him.
Also, I think it is lovely that Batman will forgive Dick for the Blockbuster affair, but he will UNDER NO CIRCUMSTANCES forgive anyone for hurting his “son”, not even Dick. Batdad FTW.