hahaha, well, it isn't so much that he is a dick to him because he feels like it. Bruce Wayne eventually adopts Dick Grayson, but, as Dick grew older, he and Bruce clashed on things. Dick had one way of doing things, Bruce had another way.
Dick is kinda cawky, lol, and Bruce generally worries about him and doesn't want him to get hurt. In the end, though, it's Bruce's fault because he was the one who asked if Dick wanted to be his sidekick.
Think of it as more of a stern father being upset at his son.