Why is he so mean to us还是why he is so mean to us哪个是对的?请解释一下相

Why is he so mean to us还是why he is so mean to us哪个是对的?请解释一下相关的语法,

My Chinese Teacher
A teacher is one who not only better our knowledge but also better our mind unselfishly.Those who are not responsible,not caring,and money-driven can never be called teachers.A true teacher is always in pursuit of three things:imparting knowledge,dispersing their confusions and shaping their characters.In this definition,teachers are rare.A teacher,my junior middle school Chinese teacher,a teacher of knowledge,a teacher of integrity,and a teacher of broad mind have casted his influence on his every student,and he is not probably a successful teacher in common sense but absolutely a good one.
As for teaching,true teachers may differ in their styles of teaching,but they are the same in their responsibleness,with my Chinese teacher a no exception.When other teachers were absent-minded on the desciplines of the class,he was still persistent on that as if he was the head teacher.When the exam named us beatniks,we gradually regreted that we had not listen to him.When I was suffering from the laughings and the criticism,he was the only one who trusted,helped and encouraged me.A true teacher ,one of integrity and sincerity usually does not have a stong desire for wealth,fame and power,for he or she is always thinking about how to spread the students knowledge,how to educate them,and how to help them grow better.He never smokes,because he know this habit may set a bad example to his students; he never cares his position in the school,for he fears that student may become mean in the future; he never gives in before authority,as he is afraid that students may become cowards in their long run for truth; he can always sing,play violin and read books,for he believe these are gifts for students in their life.
Now some of his students are scientists,for he taught them pursuing truth; some are civil servants,for he taught them devoting; some are bussiness men and women,for he taught them that life should be colorful; and I am a teacher,for his behaviors told me the true mission of a teacher.Many may have already forgot his name; however once asked who is their best teacher,they will chorus:our junior middle school Chinese teacher.