Re: how many back talk would you take?
In my opinion it reflects very poorly on the teacher if a student is granted rank for reasons other than accomplishment. Let me state this very clearly: It is NOT a reflection on the student. It is a reflection on the teacher. It says he is not teaching properly.
Politics, niceness, economics....when someone is standing on the mat, training, that stuff is irrelevent.
I should state that I write this as a slow older student who has been passed along the path by many others over the years, people who were progressing more quickly than I. At times I've had to reassure those students that this was FINE - we don't all progress at the same rate and I never felt "passed over" inappropriately.