It's exactly what you asked for, an example of "You are wrong. You haven't learned it properly." You are also saying this kind of response (You haven't learned

It's exactly what you asked for, an example of "You are wrong. You haven't learned it properly." You are also saying this kind of response (You haven't learned it properly) is appropriate. This attitude is what turns people away. You can be honest, correct and still turn people off.