The problem with "No, because..." is that it leaves the question open, especially when the person saying "no" is trying to be especially polite. Suppose the fat

The problem with "No, because..." is that it leaves the question open, especially when the person saying "no" is trying to be especially polite. Suppose the father said, "No, I wouldn't be comfortable with that." Well, when he's not there, he can't be uncomfortable, so it's ok. Suppose he said, "No, it's illegal." Well, smoking is legal at a younger age, so that must be ok. Speeding is illegal so when the son sees the father speeding, he'll have to conclude that his father is being unfair since he breaks the law but expects his son to follow it. "No" with a condition leaves the expectation that when the conditioned is changed, the answer will also change. "No" by itself is straightforward and can't lead to false expectations.