He was the leader, many people looked up to him, and he was a role model for the youngsters. These youngsters started to follow his action, whether it was good or bad. What he said to Duan Ya might not have been heard by Yu Shun, but he must have heard it on a different occasion.
However, the context was different. He must speak to someone unrelated to the Tang Empire, but on this occasion, they were talking about the Tarriors, the soldiers of the empire. It just sounded wrong to say that to their own people.
Tang Shaoyang, however, was still surprised by how big Yu Shun had changed. This young man was quite timid, distant, yet still respectful to the others. He did not know what had happened in the last few months, but the change was too big and caught him off guard.