One of the more irritating aspects of what passes for civil-rights activism in this country is the constant clamoring for a "national conversation on race." In practice, what this amounts to is blacks accusing and whites apologizing. About a dozen years ago, President Bill Clinton explicitly called for this sort of "dialogue." Now President Barack Obama has jumped into the fray. At the close of his press conference this evening, Obama denounced Cambridge, Massachusetts police for acting "stupidly" in arresting Harvard African-American Studies Professor Henry Louis Gates Jr. on July 16 for disorderly behavior.