Owen,just to put things into perspective re professional teachers and hours worked where I come from,ie the UK,let me say that high school teachers teach 26 or so teaching periods a week.Each teaching period is of 35 or 40 or 45 minutes' duration depending on the school taught at.Though the general public think teachers don't work hard, teachers themselves will tell you that teaching,if done well,is mentally tiring.Lesson-Planning,making and marking tests/exams,attending parents' evenings,and running an extracurricular club or refereeing a sports match at weekends are additional requirements expected of teachers.
Even though Chinese students tend to show more respect to teachers than their foreign conterparts do,I reckon 40 teaching periods a week is excessive,let alone 40 clock hours.Maybe you don't know that public colleges and universities here only ask their FT's to teach 16 teaching periods/week on average,while the teaching workload at middle schools is around 20 teaching periods a week.
But some teachers who are workaholics think 40 hours,clock or otherwise,represents a fair workload. You should realise they're very much in the minority.In contrast,Chinese teachers only teach around 14 teaching periods a week at most.China doesn't need the introduction of sweat shop hours into its EFL industry in my opinion.