Funny you should say that. DD goes to French school but has 1 hour/week of English. Her English teacher says "fife" instead of "five" and "tvelfe" instead of "twelve". She is Dutch. I have not only corrected her in person, but have spoken to the school teacher and said I want DD to be in the other (native speaker) teacher's class next year.
So yes, I would and have corrected a teacher for mispronouncing certain words. I fully expect my child to be taught correctly.
Also, I would correct and have corrected a doctor if I noticed a mistake. One paediatrician told me pollen allergies don't cause hives, which I know for a fact is incorrect, having suffered this exact problem throughout my childhood. Another example would be the doctor who wanted to prescribe homeopathic "remedies" to DC. He quickly admitted that there is no proof that they work but that "parents seem to like them" 
So yes, I have corrected doctors, too. If I am wrong, they tell me I am wrong, and that is perfectly fine, too.
You must live in a strange kind of world where nobody corrects anything for fear of being perceived as rude and arrogant. Still, your choice and I wouldn't dream of telling you that you are wrong and should act like me, because that would actually be arrogant 