Isn't this a form of sabotage?

I was listening to the Tom Leykis show yesterday, and there was one female caller that called in saying that she was a democrat, but also a McCain supporter; however, in the primary in her state she voted for Hillary. But her reasoning wasn’t that she disliked Obama, or even that she liked Hillary. She figured if she could help Hillary win the nomination, that McCain would crush her in the general election.

I got pretty irritated when I heard what amounts to be political sabotage, and I feel is counterproductive to the whole political process. Shouldn’t a vote be used to support policy you approve of, and not be used as a weapon against people you dislike?

I’m just wondering if people are okay with this type of action, and if there is a general question of ethics that could be discussed in this.