That's an ethics call you have to make.
In the "no, but" approach, I see no harm in it - compliance does not result in a negative result for the other person. You're not going to do it anyway, but they're going to feel better about it than just a simple "no".
In "because I have to make copies"... your call. I wouldn't, because I'd consider this improving my result at the expense of yours.
At what point is using this kind of method just clever, and at what point is it highly manipulative and antisocial?