The matter of the outer sect Spirit Herb Garden wasn't very significant. Jiang Hao wasn't worried about what Xia Cheng would do or say.
Moreover, from the recent encounter, it was clear that Xia Cheng was someone who cherished his life. So, it was safe to assume that he wouldn't take any risks.
The reason he was causing trouble for others was because of the sudden rise in his status. He was designated as the one in charge of the Spirit Herb Garden, and others tried to stay on his good side. That went to his head, especially since no one else had higher cultivation than him.
Power was addictive, and it made people reckless. Jiang Hao faced the same problem every time he advanced to a new stage or a new realm. The allure of power and strength often made him arrogant.