Quite true. To be a professional in the world of teaching first of all requires a personality of integrity. Without that, a teacher would disqualify even if he had the right degree, a decent teacher training and experience!
Those considering you to be a "trouble maker" because of this clearly show that they are highly unprofessional themselves and should not be teachers at all!

Two points about foreign teachers being expected by their Chinese employers to teach without a valid Residency Permit. The first one is that the teachers you mention above are of course Chinese. The second point is that the FAO needn't necessarily be a teacher. He (or she) is sometimes a Chinese administrator.

It might well be that Justin has to make a decision if it's worthwhile sticking his neck out and doing the right thing, or, as he said he might well do, teach illegally for a period of up to 10 days if expected to do so by his new employer. I wouldn't condemn him for taking the latter course of action, but others might.