I deserve better!

I haven't come here for a long time, as a matter of fact, I woundn't have come here today if this thing hadn't made me so upset. Today, I went to my UK cultural class and found this teacher was teaching us nothing relates to UK cultural but for his experience from studying abroad as a poor asian student. I learned this teacher was lame since the first I attened his class, knowing he takes roll calls every week and requires us to be quiet in class, what I didn't know is that he was just another teacher who gruduated from a world-famous school in UK and who, after so many years of learning and studying in foreign country, still behaves like a mediocre, or I should say incompetent in some way. Just like today he told us what's the english phrase for "甩門", he said, in the UK, they called in "sliming", he even spell it out like having prouncing it wrong is not enough. So I raised my hand and said,"sorry sir, I am one hundred percent sure that the correct word or phrase should be 'slam' as in 'Don't slam the door!'" That was a very bold move, considering the guy on the podium received his B.A and Ph.D diplomat from Cambridge, but I just wanted to point out the truth, a incharllengeable fact. I know there must be at least half of the students in class knew that the teacher was wrong, but I don't know why they weren't saying anything. Is it really that difficult to charllenge teacher's authority and credibility now in today's Taiwanese society?