If you disprove something, you haven't necessarily proved the opposite. If you disprove something, you have indeed proved its negation. If you disapprove of an action, you do indeed approve of not doing that action (so, disapproving X is approving not-X).

(That is, when you disprefer that George be elected, you prefer the negation, that George not be elected, rather than just you do not prefer that George be elected, which is compatible with indifference.)