It was pretty nauseating to see Newt so effectively turn the crowd in such a vicious way against John King for having the temerity to question him about his apparently immoral behavior. But perhaps King could have been more effective if he had put Gingrich's ex-wife's accusation in context. After all, the debate was s ponsored by a group that includes the National Organization for Marriage, a group that has no problem judging the intimate behavior of others. It might have been more effective if King had contrasted Gingrich's views on marriage with NOM's goals. Of, course, that would have meant tangling with a sponsor.
Gingrich has, on occasion, tried to contrast his extramarital behavior with that of Bill Clinton, who he was busy impeaching during his own indiscretions, by saying that Clinton committed perjury. However, I think that was just a convenient coincidence. (I've also heard the argument that Clinton lying about his affair with Lewinsky was not technically perjury, because it was not material to the legal issue at hand.)
The question brings to mind the Anita Hill hearings, in which contrasting past injustices were pitted against each other: false sexual accusations against black men, and sexual harassment of women (which had not been a legal concept for very long.) I remember running into a neighbor at the time, (a man), who said that Clarence Thomas was getting a bum rap. I was surprised to hear this, and answered that Anital Hill was so credible.
I think a reasonable way to draw the line has to do with whether someone is hurt. If non-consensual behavior is involved, or violence, or children, or hypocrisy in the judgments of others, it becomes fair game. But does Gingrich appeal to any logical basis for a line to draw that the audience was responding to?
My personal suspicion, is that in the mind of the typical audience member, and many on the right, there a people who are considered above reproach and others who are suspect, and it has a lot to do with who is considered "one of us" and who is considered "other." And yes, I think race and other matters of origin have a lot to do with it. I think that's why the birther movement has found so many adherents, and why so many Obama opponents refuse to believe his own affirmations of Christianity. Not only is Obama black, but he has a background that includes experience with other cultures, and a father from another country.
Another possibility comes from the Santorum philosophy, which puts fertility on a pedestal above almost all else. Perhaps this makes Gingrich's status - not only as a white man - but as a heterosexual man, whose indiscretions could lead to no confusion as to the fatherhood of any child, also adds to his status of being beyond reproach. Imagine a female candidate being accused of marital infidelity on a Republican stage. I have a hard time imagining her pulling off such righteous indignation. And of course, it's hard to imagine a gay person being on the stage at all.
All of this, of course, brings to mind the old feminist saying of the personal becoming political (and therefore, private.) I think it would be good for journalists to do some thinking about where they themselves draw the line in future debates, so that questions of behavior in relationships can be asked within some reasonable context.