With the asking not telling - I find that if you reprimand with something along the lines of "I was not actually asking, I was being polite. Kill the workers please." people will very quickly learn that you are polite, but do not mistake politeness for weakness.
I always use please and thank you - I would have told the production manager who made that comment, Matthew, just because we are paying them does not mean we don't have to be polite and thankful for tasks being done promptly and well.