The trick as an instructor (i have trained as a driving istructor) is to critisise effectively. This is a black art and no doubt. You need to be able to pan your student, but not go so far as to knock what little confidence they have for a six!
What you are looking for is someone that can say also praise the good bits.
The guy I have now has a lot more confidence in my flying than I do, as him sending me solo yesterday when I didn't really want to is a testiment to. This is because I have had all the confidence kicked out of me earlier in my training, and am not that self assured at the best of times. His methods worked and I now feel 200% better about solo flying, the praise he heaped upon me was great, but was also tempered with "you screwed that up nicely" and "see, I told you, take that as a lesson learned and move on"
That is the sort of thing you want, tell you what you are doing wrong, to a point let you make the mistake in the first place, without compromising safety, to see if you can recognise it for what it is and put it right.
And a good de-brief afterwards, covering the good and bad bits, but always ending on a high note, and an overview of what you will do next time are a must.
As for calling you pathetic, someone started down that track with me once on a course, and got both sides of my tongue and was left in no doubt what I thought of his teaching methods. He was attempting to knock the stuffing out of me for a more than beligerant reason only came across a brick wall, and when asked the question "that is diabolical, who the hell taught you to do that?" got the reply " your companys other effing instructor, when you can all sing the off the same sheet have a pop, until then belt up whist you still can!!" I stopped the course there and then, and refused to pay his invoice as well. Take note, your money is valuable to you, don't waste it on some numpty that has a bad idea of motivation!!