>>280554429 (OP)Because he was still in his "dedicating his life to vengeance" stage. He was extremely focused and dedicated and because of that was far less tolerant of other people, especially if he believed they were not as dedicated as he was. He didn't know that Leorio was also coping with his own personal loss and actually was also dedicated to achieving his own noble goals. As the arc progresses and they learn more about each other, partially thanks to Him helping them to get over themselves, they get a long much better. What was once pointed jabs now become friendly banter because they both understand each other a lot better.