Nogbad, I think you are confusing me with someone else. I haven't done a search, however, so perhaps you could point me at the thread you refer to?
Readbacks:-
Once again, mistakes get made. That's why we read things back to you. You check it, and correct it if necessary. Take the second part of that away, and there's not much point in us reading it back, is there? If someone were accidentally to thumb the PTT as you are TXing your instructions to us, partially blocking out one word, and we think we heard FL310 when you said FL210, we read back FL310. You didn't hear the crossed transmission. You don't check the readback. Who is then to blame for the level bust?
Yes, ATC instructions INSIDE CONTROLLED AIRSPACE are mandatory. UNLESS there is a reason why the aircraft is unable to comply, or doesn't hear them, or safety dictates another course of action, or blah blah blah... I say again, we are not there just to do your bidding. If I have rapid decompression and need urgently to descend below FL100 and you tell me to maintain for the next 5 miles, my reply to you will be "NUTS".
I never said, or implied, that ATC instructions are given to us "for the hell of it." Such an idea is total nonsense, and treats professional pilots as if they were children. Similarly, to say "Please report everything you're asked too." That is also treating pilots like children. Can you imagine how that rattles cages? Can you now understand the vehemance of my post?