Ten days ago, I noted the reckless assertion of Barack Obama’s former pastor that the United States government had deliberately engineered AIDS to kill blacks, but I tried to put it in context by citing a poll showing that 30 percent of African-Americans believe such a plot is at least plausible.

My point was that the Rev. Jeremiah Wright is not the far-out fringe figure that many whites assume. But I had a deluge of e-mail from incredulous whites saying, in effect: If 30 percent of blacks believe such bunk, then that’s a worse scandal than anything Mr. Wright said.

It’s true that conspiracy theories are a bane of the African-American community. Perhaps partly as a legacy of slavery, Tuskegee and Jim Crow, many blacks are convinced that crack cocaine was a government plot to harm African-Americans and that the levees in New Orleans were deliberately opened to destroy black neighborhoods.

White readers expressed shock (and a hint of smugness) at these delusions, but the sad reality is that conspiracy theories and irrationality aren’t a black problem. They are an American problem.