Though most likely these words are not those that are spoken, quite often "Do what I say or else" is the implication. It might be covered up by words like "can you do this for me" or "it's the least you could do", but if you search deep enough you will hear an ultimatum in within their voice. Often this form of blackmail can come as a subliminal threat to end the relationship or even to take away something they control. But, fear not, this sort of attitude arises out of fear and is really a last resort for the individual's childish nature to take hold of their body, almost like a parasite. The best thing you can do in such a situation is look upon the attitude of this person (or yourself if that is the case) and smile at it just as you would the antics of a child.