It's only natural to anger Giant Wu.
Young Master Nan also knew that Wu Jinliang had once gone against Gong Shaoci for Duan Xiangmei, so he protected Duan Xiangmei.
The reason why Wei Mo wanted Wu Jinliang to know that if Shi Chun didn't turn himself in, Duan Xiangmei would be the first to be executed was because he knew Wu Jinliang had fallen out with Gong Shaoci over Duan Xiangmei.
Since Duan Xiangmei holds some significance to you, Wu Jinliang, now that Duan Xiangmei is in my hands, you, Wu Jinliang, naturally become a good leverage to pressure Shi Chun.
Sure enough, Wu Jinliang immediately got riled up, wanting to send a warning message, but knew he couldn't, or else he'd lose room to maneuver.
The reasoning was simple; once it's proven you've contacted them, the other side might use the weak point they've seized to force him to show up immediately.
Now he could only pretend he saw nothing; the other side's uncertainty whether you've seen it would slow their actions.
