To echo what Rob (and Henry) have said, it’s worth drawing a distinction here. Reasonable people can argue about “outing” in the sense of, say, a newspaper publishing reliable information that a politician with rabidly anti-gay views is in fact gay or lesbian. While I agree with Rob that I don’t have a lot of sympathy for a politician who wants to make the consensual sexual choices of adults a major political and public policy issue and then gets outed, I’m not really crazy about even this. Homophobic positions are equally bad on the merits whether they’re advanced by heterosexuals or not, and a cursory examination of justifications for discussing various irrelevant aspects of the lives of public officials will show that “hypocrisy” justifications tend to become pretty weak tea — it gets so that anybody who’s ever appeared in public with their spouse is completely fair game. Basically, I would say that I probably wouldn’t publish such information in most cases and don’t think it’s really relevant to anything, but there’s at least a fair argument to be made in such cases.
But the anti-McConnell ad is another matter entirely, completely beyond any reasonable justification. The salient fact is that the ad is disgustingly homophobic. It’s just directly trying to mobilize anti-gay sentiment against McConnell, which is beyond any progressive pale. Fighting bigotry with bigotry isn’t a defensible position, and of course the ad isn’t even trying to do the former. Nobody should want to unseat McConnell this way.