A great many people believe that it is wrong to date anyone whose political views differ significantly from their own. James Kirchick challenges that view in this article (hat tip Amber Taylor, whose post led me to Kirchick's article by a circuitous route). Kirchick's piece focuses on the reluctance of many gay liberals to date gay conservatives and libertarians like himself. But the underlying issue goes beyond the gay community.
In general, I am sympathetic to Kirchick's view that much of the reluctance to date across ideological lines stems from unjustified intolerance. However, I also have some reservations. First, the reasons for agreement.
I. Why People Overestimate the Undesirability of Cross-Ideological Dating.
I suspect that the most important reason for excessive reluctance to date across ideological lines is overestimation of the extent to which people's political views dictate other aspects of their lives. Ideologies that claim that "the personal is political" (a left-wing slogan that has important analogues in parts of the "family values" right) exacerbate this tendency. In reality, most people's views on public policy have only a modest impact on the way they live their lives. For example, my libertarian views are vastly different from those of most liberal law professors. But the way I live my life when I'm not writing about ideological subjects is very similar to the way most of them live theirs.
An exception are those people who embrace ideologies that really do dictate the conduct of all aspects of their lives, such as members of certain cult groups, or communists in the days when belonging to the Party meant belonging to the sort of all-encompassing group depicted by Richard Wright in "I Tried to be a Communist." However, most people in the US today don't try to inject ideology into every aspect of their lives.
The second-biggest reason is probably the perception that certain political views are not just mistakes, but proof that the person who holds them has corrupt values. As I will argue below, this is occasionally true. But it's not true nearly as often as many believe. Partisans and ideologues routinely overestimate the extent to which political disagreements reflect differences in fundamental values rather than divergent evaluations of the best way to achieve the same or similar values. A very high proportion of the disagreements between conservatives, liberals, and libertarians in the US today fall into the latter category. There are some important exceptions, such as the conflict over abortion. But even these partly turn on divergent views of how to apply shared values to particular cases. For example, both sides in the abortion debate claim to value both life and freedom; they differ, however, over the threshold at which a person acquires a right to life sufficient to override another person's right to bodily autonomy. Moreover, at least some of the issues where adherents of the three major US ideologies really do diverge on basic values have arisen in part because the issues in question are genuinely hard (as the abortion issue surely is). If so, one can embrace the wrong values on that issue without necessarily being a moral cretin in general.
II. Defensible Limits of Political Tolerance in Dating.
At the same time, there are genuine reasons to avoid dating people with certain types of political views. Some views really are an indication of moral depravity. James Kirchick is willing to date liberals. But he probably would not date a racist or a Nazi - and for good reason. Similarly, I would not date a communist or an apologist for that system. Claims that "anyone who believes X must be evil/depraved/immoral" are made far more often than is justified. But that doesn't mean that they are never true.
There is also a more pragmatic case against cross-ideological dating. Even if you don't think that disagreement with your political views is a sign of immorality, strong disagreement can be a point of conflict in a relationship - especially if one or both partners are intolerant or don't like to have their views questioned. The problem is likely to be heightened if both people care intensely about their ideologies or if one of them is a committed activist.
Whether or not such pragmatic considerations are weighty enough to prevent a relationship will vary from case to case. However, it is important to recognize that they should in fact be judged on a case by case basis. If the potential date's views are not intrinsically evil (a category that should be defined narrowly), the mere fact of political disagreement should usually not be viewed as a categorical bar to dating, but merely as one factor to be weighed against others. For many people who are strongly interested in politics, discussing issues with someone who doesn't agree is actually sometimes more interesting and stimulating than just getting an echo chamber of your own views.
UPDATE: Commenters and others will inevitably wonder whether my views on this issue are the result of painful personal experiences of the kind described in Kirchick's article. I'm not going to discuss my personal life in detail here (very disappointing, I know...). But I will say that the answer to this question is "no." I have never been rejected by anyone I was seriously interested in because of ideological disagreement; nor have I have ever had a relationship that failed for that reason (though I have had cross-ideological relationships that fell apart for unrelated reasons).