It depends on the question. If I had asked, “Would you like my abuse to stop?”, then “No sir” would be a perfectly acceptable answer.
If they did have the audacity to say no to me, then clearly they need to be punished further.
If they were not comfortable or unable to do a task, they would need to reply with our set safety words (yellow, red) to be taken seriously. Otherwise, thier pleas for mercy would be ignored.