Master Sun thought that he was disrupting the class, and Xiao Jingkong argued that Master Sun was misleading the students. To prove his point, he set a trap for Master Sun, throwing him ten arithmetic problems in one go.
Master Sun couldn't solve a single problem.
If he couldn't solve them, it means Master Sun's scholarship was not solid enough. If his scholarship was not solid enough, it shows there's an issue with the teaching methods of Master Sun, and therefore he is indeed misleading the students.
This was Xiao Jingkong's logic, but in reality, it's not fair to generalize like this. Master Sun was unable to solve those problems, probably because they were beyond his realm of knowledge. It is not fair to say that the concepts within Master Sun's realm are also wrong.
Unfortunately, Xiao Jingkong was the class leader, and when he called, everyone responded, and the whole class followed his lead in making trouble.