I completely understand your reasoning . . . for primaries. You should vote for the person that best represents your values in every election. But, if it is a general election and both candidates are pro-choice, wouldn't you rather make sure the one that agrees with you on 80% of the issues gets in rather than the one that agrees with you on 10% of the issues???
I probably would hold my nose in the GENERAL election and vote for Rudy, only because I'd trust him more on security issues than Hitlery.