Anyway the moral of the story is that although our teacher might speak some partial truth ,it is not wise to trust them 100 percent as humans simply make mistakes ,
for example ,how do you tackle a racist person
ans:speak fluent english and ask them if they know how to speak mandrin.
1.if you met a nice racist bully which is however ironic ,how can a bully be nice .He /she will let you off
2.if it was a nasty person ,he/she might think that you are picking a fight and there goes your two front teeth.
3.what has chinese got to do with them ,why must they speak it anyway ,thats being a complete show off(it is the best way to pick a fight)they can show you a pioroutte and on and on you go ,neverending childishness

suggestion ,shun such people ,learn some kind of self defence ,call the cops or something ,thats so much easier.